ROCK 

EXCAVATING 
AND    BLASTING 


By 
J.    J.    COSGROVE 


Author    of 

"PRINCIPLES  AND  PRACTICE  OF  PLUMBING" 
"SEWAGE  PURIFICATION  AND  DISPOSAL" 

"HISTORY  OF  SANITATION" 

"WROUGHT  PIPE  DRAINAGE  SYSTEMS" 

"PLUMBING  ESTIMATES  AND  CONTRACTS" 

"DESIGN  OF  THE  TURKISH  BATH" 

'SANITARY  REFRIGERATION  AND  ICE-MAKING" 

"SANITATION  AND  HYGIENE" 


Published     by 

Rational    3?trc    proofing    Company 

Pittsburgh,     U.    S.    A. 


COPYRIGHT    1913.    J.    J.    COSGRC 


c> 

PREFACE 


HIS  work  was  called  forth  by  a  real 
and  urgent  demand  for  a  book  that 
would  help  the  young  engineer,  the 
superintendent,  the  rockman  and 
miner  to  understand  the  mysteries 
of  explosives;  how  to  handle  them;  and  how  to 
get  the  best  results  in  the  various  kinds  of  rock 
excavating. 

It  is  a  well-known  fact  that  schools  of  engineer- 
ing teach  the  design  of  engineering  works,  but 
not  their  construction.  A  few  strokes  of  the 
pen  show  how  a  tunnel  is  to  be  driven  through  a 
mountain,  but  there  is  nothing  shown  on  the 
drawings  or  taught  in  school,  that  will  point  out 
how  the  work  is  to  be  accomplished.  This  part  is 
left  for  the  contracting  engineer  to  work  out  for 
himself,  and  the  young  engineer  in  charge  of 
the  work,  if  he  has  had  no  previous  experience, 
must  pick  it  up  as  he  goes  along  from  the  rock- 
men  in  charge  of  the  blasting. 

As  most  of  the  graduates  of  engineering  col- 
leges follow  the  contruction  branch  of  their  call- 
ing, and  in  the  course  of  their  work  are  soon  put 
in  charge  of  rock  excavating,  either  open-cut 
work,  tunnel  driving  or  shaft-sinking,  this  work 
will  be  found  invaluable  to  them  as  well  as  in  the 
class  room,  and  in  the  hands  of  anyone  interested 
in  quarrying  or  blasting  rocks  or  other  hard  ma- 
terials. 

It  is  believed  that  by  following  the  text  a  person 


wholly  unfamiliar  with  blasting  and  explosives 
could  intelligently  superintend  rock  excavating  or 
do  it  himself.  Text  and  illustrations  show  how 
to  drill  bore  holes  to  get  different  results;  how 
to  charge  the  bore  holes ;  how  to  drive  a  tunnel ; 
how  to  sink  a  shaft ;  blasting  in  quarry- work  and 
open-cut  excavating;  care,  handling  and  storage 
of  explosives ;  and  the  tools  and  machines  required 
in  rock  excavating. 

A  copy  of  this  book  should  be  found  on  the 
shelves  of  every  library.  It  will  also  be  found 
invaluable  at  mines  and  quarries,  in  the  class  room 
of  engineering  colleges,  and  in  the  offices  of  en- 
gineers, architects  and  contractors. 

J.  J.  COSGROVE. 

Philadelphia,  Pa.,  September,  1913. 


PUBLISHERS'  NOTE 

HIS  is  an  age  of  vocational  training.  The 
old  system  of  apprenticeship  having  passed 
away  left  a  lack  of  skilled  workers  without 
which  no  nation  can  be  truly  prosperous. 
Schools  and  colleges  have  been  established 
to  supply  this  lack  of  technical  training, 
but  schools  and  colleges  can  help  only  those 
who  come  to  their  doors,  thirsting  for  knowledge. 

The  great  host  of  workers,  however,  the  very  back- 
bone of  the  industrial  Commonwealth,  are  left  to  shift  for 
themselves,  and  carve  out  of  the  hard  rocks  of  experience 
their  own  futures  and  fortunes.  Such  a  system  injures 
not  only  the  worker,  but  the  employer  and  State  as  well; 
and  within  recent  years  large  industrial  concerns  have 
turned  their  attention  toward  providing  vocational  training 
for  all  those  interested  in  their  calling. 

Railroads  not  only  have  traveling  instructors  and 
courses  of  study  for  the  trainmen,  but  some  of  them  have 
schools  for  apprentices  in  their  shops;  and  most  of  the 
railroads  do  not  stop  at  that,  but  reach  out  to  help  the 
farmers,  manufacturers  and  tradesmen  along  their  lines  to 
produce  bigger  crops,  increase  their  output,  and  in  every 
way  improve  their  methods  and  make  greater  profit. 

Manufacturers  of  type-setting  machines  maintain  free 
schools  to  teach  the  care  and  operation  of  their  machines. 
Manufacturers  of  plumbing  and  heating  goods  have  text- 
books and  free  publications  of  an  educational  nature  pre- 
pared, to  help  and  instruct  those  connected  with  their  call- 
ing; and  all  along  the  line  is  found  the  same  awakening 
to  the  importance,  the  duty,  and  the  benefit  of  a  like  course. 
In  keeping  with  the  spirit  of  the  times,  we,  as  the 
pioneer  manufacturers  of  fire-proofing  materials  for  build- 
ings, and  the  largest  manufacturers  in  the  world  of 
NATCO  hollow  tile  building  blocks,  have  accepted  the  re- 
sponsibility thus  imposed  upon  us,  to  do  our  share  towards 
furnishing  reliable  and  readily-available  information  re- 
garding all  phases  of  building  construction.  In  carrying 
out  this  undertaking  our  monthly  magazine,  BUILDING 
PROGRESS,  was  started,  and  the  work,  "Rock  Excav- 
ating and  Blasting,"  first  appeared  in  its  pages  as  a  serial 
article.  The  value  of  the  information  contained  in  the 
series  prompted  us  to  put  it  out  in  more  enduring  form, 
suitable  for  ready  reference;  and  this  we  do  just  as  it  left 
the  author's  hands,  without  one  word  of  advertising  any- 
where in  the  book. 

NATIONAL  FIRE-PROOFING  COMPANY, 

Pittsburgh,  Pa. 


TABLE  OF  CONTENTS 

eg?         <ty 

PAGE 

FORCE  AND  DIRECTION  OF  A  BLAST  1 

SINKING  SHAFTS  THROUGH  ROCK  17 

TUNNEL  DRIVING  23 

ROCK- DRILLING  TOOLS  AND  MACHINERY   35 

OPERATING  DRILLING  MACHINES  45 

ROCK-DRILL  BITS  OF  STEEL 51 

HAMMER  DRILLS   69 

STONE  CHANNELERS  75 

POWDER    91 

CHARGING  DRILL  HOLES  WITH  POWDER 107 

DYNAMITE 117 

METHOD  OF  THAWING  DYNAMITE  127 

DETONATORS  FOR  EXPLODING  CHARGES  147 

FIRING  BLASTS  BY  ELECTRICITY  157 

HANDLING  AND  STORING  EXPLOSIVES  .                         .  173 


LIST  OF  TABLES 


TABLE.  PAGE 

I.  Size  of  Drill  Holes   ........................  12 

II.  Weights  and  Specifications  of  Rock  Drills  ____  38 

III.  Weights  and  Specifications  of  Rock  Drills  ____  56 

IV.  Air  Required  to  Run  Rock  Drills   ...........  64 

V.  Factors  for  Various  Altitudes  and  Pressures.  .  66 

VI.  Capacities  of  Hammer  Drills    ...............  70 

VII.  Specifications  of  Stone  Channelers  ...........  85 

VIII.  Specifications  of  Channeling-Machine  Steels...  87 

IX.  Size  of  Drill  Holes  for  Different  Weights  of 

Explosives    .............................  105 

X.  Size,  Number  and  Weights  of  Tamping  Bags.  .  116 

XI.  Sizes  and  Weights  of  Dynamite  Cartridges.  .  .  .  123 

XII.  Sizes  of  Blasting  Caps    ....................  148 

XIII.  Name  and  Use  of  Fuses   .                                    .  152 


LIST  OF  ILLUSTRATIONS 


FIG.  PAGE 

1.  Hole  Made  by  "Grip"   Shot   ..................  2 

2.  Inclination  of  Drill  Hole  for  "Grip"  Shot   .....  3 

3.  Effect  of  Blast  in  Rock  Having  Two  Free  Faces  5 

4.  Effect  when  Charge  is  Equal  Distance  from  Two 

Free  Faces    ...............................  6 

5.  Showing  Terms  Used  in  Blasting  ..............  8 

6.  Bench  Work  in  a  Quarry   ....................  9 

7.  A  "Chambered"  Drill  Hole  ....................  11 

8.  Effect  .of  Multiple  Blasts    ....................  13 

9.  Rock  Removed  by  Multiple  Blast  ..............  15 

10.  Arrangement  of  Drill  Holes  in  Shaft  Sinking.  .  18 

11.  Deep  Drill  Holes  for  Shaft  Sinking  ...........  20 

12.  Rock  Drilling  in  Small  Tunnel—  Soft  Rock  .....  24 

13.  Diagram  of  Drill  Holes  in  Tunnel—  Soft  Rock.  .  .  25 

14.  Drill  Holes  for  Small  Tunnel  in  Hard  Rock  .....  26 

15.  Drill  Holes  Near  Fissures  or  Faults    .........  29 

16.  Method  of  Working  Large   Tunnel    ...........  31 

17.  Rock   Drill  on   Tripod    .......................  36 

18.  Rock  Drill  on  Quarry  Bar  ....................  40 

19.  Mining  Column  or  Shaft  Bar  .................  42 

20.  Sand  Pump    .................................  47 

21.  Perspective  View  of  Rock-Drill  Steel   ..........  52 

22.  Drill  Steel  for  Hard  Rock  ....................  52 

23.  Drill  Steel  for  Soft  Rock  .....................  53 

24.  Length  of  Rib  on  Drill  for  Soft  Rock  ..........  53 

25.  Cutting  Edge  on  Drill  Steel  for  Soft  Rock  ......  54 

26.  "X"  Bit  Drill  Steel   ..........................  55 

27.  A   Swage    ...................................  62 

28.  A  "Sow"  ....................................  62 

29.  Cross-Shaped   Dolly    ..........................  62 

30.  X-shaped  Dolly  ..............................  62 

31.  A  Flatter   ...................................  62 

32.  Spreader    .....................  62 


33.  Swage  for  Anvil 62 

34.  Swage  for  Hammer  62 

35.  Hammer    Drill    72 

36.  Steel  for  Hammer  Drill 73 

37.  Method  of  Using  Hammer  Drill 74 

38.  Simplex  Channeling  Machine    77 

39.  Duplex  Channeling  Machine   79 

40.  Channeler   Steels   for  Marble    81 

41.  Three-piece   Gang  Drill   Steels  for  Channeler...  81 

42.  Gang  Drill  Steels  for  Channeling  Slate 81 

43.  Z-Shaped  Channeling  Steel  for  Fissured  Rock.  . .  81 

44.  Channeled  Walls  of  Chicago  Drainage  Canal 82 

45.  Quarrying  Dimension  Stone  with  Channeler.  ...  83 

46.  Group  of  "A"  Powders    93 

47.  Group  of  "B"  Powders   94 

48.  Method  of  Charging  Drill  Hole   110 

49.  Cartridge  of  Dynamite   123 

50.  Kettle  for  Thawing  Dynamite 128 

51.  Thawing-Box   for   Dynamite    130 

52.  Thawing-House  for  Dynamite  133 

53.  Steam   or  Water-Heated   Thawing-House    138 

54.  Dynamite    Tray    140 

55.  Blasting  Cap 148 

56.  Coil  of  Fuse    151 

57.  Fuse  Attached  to  Blasting  Cap   152 

58.  Blasting  Cap  in  Dynamite  Cartridge   153 

59.  Fuse  Attached  to  Side  of  Cartridge 154 

60.  Fuse  Primed  for  Lighting 155 

61.  Lampwick  Primer  for  Fuse   156 

62.  Section  of  Electric  Fuse 158 

63.  Waterproof  Fuse  for  Submarine  Work 159 

64.  Electric  Fuse  Attached  to  Cartridge   160 

65.  Two  Electric  Fuses  in  One  Drill  Hole  161 

66.  Two-Wire   Circuit  for  Multiple  Blasts    162 

67.  Three- Wire  Circuit  for  Multiple  Blasting   163 

68.  Joint  for  Electric  Wires 164 

69.  Two-Post  Blasting  Machine    166 

70.  Three-Post  Blasting  Machine   167 

71.  Portable  Dynamite  Magazine   176 

72.  Detail  of  Portable   Magazine    .178 


ROCK 

EXCAVATING 
AND    BLASTING 


PART  I. 

DRILL  HOLES 

*        * 
CHAPTER  I. 

FORCE  AND  DIRECTION  OF  A  BLAST. 


IRECTION  OF  A  BLAST.—  There  is  a 
popular  belief  that  different  explo- 
sives behave  differently  when  fired, 
some  expending  their  forces  down- 
wards, others  sidewise,  while  still 
others  have  a  lifting,  or  upheaving,  direction. 
Nothing,  however,  could  be  further  from  the 
truth.  All  explosions  of  blasting  agents  of  what- 
ever composition  follow  the  line  of  least  resist- 
ance, although  more  or  less  execution  is  done 
along  the  line  of  greatest  resistance.  For  ex- 
ample, if  a  heavy  charge  of  an  explosive  be  fired 
close  to  a  stone  slab  standing  on  edge  along  the 

1 


Rock    Excavating    and    Blasting 


side  of  the  charge,  the  slab  would  be  shattered. 
It  would  likewise  be  shattered  if  it  were  below 
the  charge  or  above  it  at  the  time  of  firing. 
While  the  direction  of  a  blast  cannot  be  changed, 
different  effects  can-  be  produced  by  the  use  of 
different  explosives,  or  by  varying  the  charge,  as 
will  be  explained  later. 

The  form  of  cavity  produced  when  a  single 
charge  of  explosives  is  fired  in  a  vertical  drill  hole 

is  shown  in  Fig.  1. 
Following  the  line 
of  least  resistance, 
the  blast  would  pro- 
duce a  cone-shaped 
cavity,  the  size  of 
the  cavity  depending 
upon  the  strength 
and  size  of  the 
charge.  If  the 
strength  of  the  explosive  or  the  size  of  charge 
were  not  sufficient  to  dislodge  a  large  amount  of 
rock,  still  the  cone  shape  would  be  adhered  to, 
only  the  cone  in  that  case  would  be  smaller, 
for  instance,  that  shown  by  the  dotted  lines.  In 
case  too  small  a  charge  or  too  weak  an  explosive 
were  used,  a  blowout  would  occur,  carrying  with 
it  a  small  cone-shaped  fragment  from  near  the 
mouth  of  the  drill  hole.  In  that  case  the  blast 
would  act  just  as  a  charge  of  powder  in  a  gun — 
it  would  simply  blow  out  the  tamping. 

INCLINATION  OF  DRILL  HOLES. — A  vertical  posi- 

2 


Fig.    1. 
Hole  Made  by  "Grip"  Shot. 


Rock    Excavating    and    Blasting 


tion  is  the  worst  position  in  which  a  drill  hole 
can  be  made  for  a  key-hole  or  cut-out  blast,  for 
the  reason  that  there  is  only  one  free  face  for 
the  force  of  the  blast  to  break,  as  the  downward 
and  side  pressures  are  opposed  by  solid  rock. 
Action  and  reaction  being  equal  but  opposite,  it 
follows  that  in  a  cavity  made  by  firing  a  charge 
of  explosive  in  a  vertical  drill  hole,  the  resultant 
of  all  the  forces  would  be  along  the  line  of  the 
drill  hole,  or  from  the  apex  of  the  cone  to  the 
center  of  the  base,  which  would  represent  the  line 
of  least  resistance.  That  being  true,  a  better 
method  is  to  drill  the  hole  at  an  angle  as  shown 
in  Fig.  2.  This  brings  the  drill  hole  away  from 
the  line  of  least  resistance  and  gives  an  enlarged 
free  face  for  the  explosive  to  act  upon,  with  the 
result  that  there  is  less  danger  of  a  "blow  out," 
and  greater  amount  of  rock  will  be  dislodged. 

The   limiting   inclination   of  the   drill   hole   is 
45  degrees  with  the  free  face.    With  a  hole  of  less 

inclination  less 
rock  will  be 
broken  and  the 
amount  will 
grow  less  as 
the  hole  ap- 
proaches the 
free  face,  until, 
if  discharged 
at  the  surface, 


Fig.  2. 
Inclination  of  Drill  Hole  for  "Grip"  Shot. 


the  result  would  be  practically  zero. 

This  inclination  of  a  drill  hole  is  important  to 
3 


Rock    Excavating    and    Blasting 


keep  in  mind,  for  it  is  the  starting  point  for  all 
plane  surfaces.  In  the  starting  of  an  excavation 
for  a  cellar,  for  instance,  beginning  at  the  center 
a  grip  shot  of  this  description  could  be  fired; 
then  with  this  cavity  to  work  from  the  drills 
could  be  started  radiating  in  all  directions,  using 
the  surface  for  one  free  face,  and  the  cavity  for 
another,  and  inclining  the  drill  in  whatever  direc- 
tion necessary  to  get  the  best  result. 

FREE  FACES  IN  BLASTING.  —  The  more  free 
faces  exposed  in  the  rock  to  be  removed  the  more 
easily  can  it  be  blasted.  This  is  particularly  im- 
portant where  the  rock  taken  out  is  to  be  used 
for  building  purposes,  for  it  can  be  taken  out 
without  shattering  it  to  the  same  extent  that 
would  follow  blasting  with  only  one  free  face. 
Further,  the  cost  is  kept  down  considerably  by 
the  greater  ease  of  quarrying  from  rock  having 
two  or  more  free  surfaces. 

The  effect  of  a  blast  in  rock  having  two  free 
faces  is  shown  in  Fig.  3.  If  the  charge  were 
placed  where  shown  in  the  illustration  and  the 
top  were  the  only  free  face  exposed  the  blast 
would  remove  the  rock  from  a  cone  indicated  by 
the  triangle  a  b  c.  If,  on  the  other  hand,  the  top 
were  solid  rock  and  the  side  face  free  the  cone 
removed  by  the  blast  would  be  represented  by 
the  triangle  a  b  d.  In  this  case,  however,  both 
the  top  and  side  faces  are  free,  and  the  rock  re- 
moved by  the  blast  may  be  indicated  by  the  dotted 
lines  which  almost  parallel  the  solid  line  c  b  d. 
It  will  be  noticed  that,  with  two  faces  exposed,  the 

4 


Rock    Excavating    and    Blasting 


blast  will  remove  practically  twice  the  quantity 
of  rock  that  would  be  displaced  with  only  one 
face  free — that  is,  it  will  if  the  charge  is  of  the 
right  size  and  located  equally  distant  from  both 
faces,  so  that  the  bounding  surface  of  the  two 
craters  that  would  be  formed  by  different  blasts 


Fig.  3. 
Effect  of  Blast  in  Rock  Having  Two  Free  Faces. 

in  single  face  explosions  will  be  along  the  line  a  b. 
If  the  charge  were  located  as  shown  in  Fig.  4  at 
unequal  distances  from  the  faces  of  rock,  the 
charge  acting  on  each  face  separately  would 
break  the  cones  a  b  c  and  d  b  e,  respectively,  the 
wedge-shaped  piece  indicated  by  shaded  lines  not 

5 


Rock    Excavating    and    Blasting 


being  included  in  either.  When  the  two  faces  are 
exposed,  however,  part  of  the  force  of  the  blast 
is  used  to  break  down  the  rock  in  this  wedge- 
shaped  piece,  and  the  crater  actually  broken  out 
is  that  bounded  by  the  dotted  lines  /  b  g. 

It  will  be  observed  that  in  figuring  the  rock 
removed    by    a    charge    the    cone-shaped    crater 


f   '    -    c 


Fig.  4. 
Effect  when  Charge  is  Unequal  Distance  from  Two  Free  Faces. 

formed  by  a  single  drill-hole  blast  is  used  as  a 
base,  and  from  this  the  amount  of  rock  that  can 
be  broken  down  by  a  single  shot  is  calculated  or, 
rather,  judged.  The  greater  the  number  of  free 
faces  the  greater  the  amount  of  rock  that  can  be 
broken  down  by  a  single  shot,  or,  in  other  words, 
a  smaller  charge  can  be  used  to  break  down  a 

6 


Rock    Excavating    and    Blasting 


certain  amount  of  material  when  there  are  two 
or  more  faces  exposed  than  when  there  is  only 
one  free  face;  but  the  amount  of  rock  loosened 
will  not  be  proportional  to  the  number  of  free 
faces. 

In  drilling  for  a  blast,  where  two  or  more  free 
faces  are  exposed,  it  may  be  taken  as  a  rule  that 
the  longest  line  of  resistance,  or  the  distance  back 
from  any  one  of  the  free  faces,  should  not  be 
greater  than  one  and  a  half  times  the  shortest 
line,  or  line  of  least  resistance,  if  the  maximum 
effect  of  the  explosion  is  to  be  obtained.  Further, 
it  is  better,  if  possible,  to  so  place  the  charge 
that  the  shortest  line,  or  line  of  least  resistance, 
will  be  horizontal  and  the  longest  line  vertical, 
so  that  the  weight  of  rock  loosened  by  the  blast 
will  help  break  down  the  mass. 

TERMS  USED  IN  BLASTING.  —  The  terms,  or 
names,  used  in  quarry  work  and  blasting  can  be 
readily  understood  by  a  reference  to  Fig.  5,  which 
shows  a  bench,  or  open  ledge,  of  rock  having  two 
free  faces,  one  the  top  surface  and  the  other  the 
front  face.  It  will  be  noticed  that  the  new  face 
of  the  bench  of  rock  is  some  distance  back  of  the 
bore  hole,  a  certain  amount  of  rock  being  loosened 
from  that  place  at  each  blast.  The  "burden  of 
rock"  is  the  mass  loosened  or  broken  down  by  the 
charge,  while  the  line  of  least  resistance  in  this 
case  is  the  shortest  distance  from  the  center  of 
the  charge  of  explosive  to  a  free  face. 

In  open-cut  work  the  best  and  most  economical 
7 


Rock    Excavating    and    Blasting 


plan  is  to  break  the  rock  into  regular  benches. 
This  rule  holds  true  whether  quarrying  for  the 
stone  itself  or  simply  breaking  out  the  rock  to 
remove  it.  When  broken  into  regular  benches 
the  condition  'of  the  rock  can  be  carefully  ob- 
served, the  subsequent  bore  holes  can  be  more 
intelligently  placed  and  the  machine  drills  can  be 
more  easily  set  up  and  handled. 


Fig.  5. 
Showing  Terms  Used  in  Blasting. 


In  Fig.  6  can  be  seen  regular  bench  work  in  a 
quarry,  with  men  at  work  with  "Plug"  drills, 
cutting  plug  and  feather  holes  for  splitting  out 
the  blocks.  The  smooth  deck  space  on  the  several 
benches  show  clearly  how  much  easier  this  rock 
would  be  to  work  upon  than  a  space  of  similar 
size  broken  into  irregular  surfaces. 

8 


Rock    Excavating    and    Blasting 


Rock    Excavating    and    Blasting 


DIAMETER  AND  DEPTH  OF  DRILL  HOLES. — There 
is  an  intimate  relation  between  the  diameter  and 
depth  of  a  drill  hole  used  in  blasting.  The  drill 
hole  should  not  be  filled  more  than  half  full  of 
the  explosive,  while  as  a  general  rule  the  charge 
should  be  about  twelve  times  as  long  as  the  diam- 
eter of  the  bore  hole  at  the  bottom.  For  instance, 
a  bore  hole  2  inches  in  diameter  at  the  bottom 
would  have  a  charge  of  about  24  inches  in  length. 
The  diameter  of  the  bore  hole  should  likewise  be 
proportioned  to  the  line  of  least  resistance,  for 
if  a  drill  hole  of  small  diameter  be  carried  down 
too  deep  in  the  rock,  or  too  far  from  the  free 
face,  the  charge  will  fail  to  break  down  the  mass 
and  a  blow-out  shot  will  result.  Ordinarily  a 
hole  sufficiently  large  can  be  made  by  using  a 
larger  drill  than  the  ordinary  when  the  drill  hole 
is  to  be  extended  to  unusual  depths.  This  in- 
creased diameter  of  the  hole,  which  by  doubling 
the  diameter  quadruples  the  charge  it  will  accom- 
modate, will  suffice  for  ordinary  blasting  opera- 
tion. Sometimes,  however,  in  quarry  work,  pre- 
paring sites  for  buildings,  in  side  cuts  of  earth- 
work, railroad  and  other  engineering  works,  drill 
holes  twenty  feet  or  more — sometimes  as  much 
as  sixty  feet — in  depth  are  made  and  hollowed 
out  at  the  bottom  to  form  a  chamber  or  pocket, 
into  which  several  kegs  of  powder  or  other  explo- 
sive are  introduced  to  charge  for  the  breaking- 
down  blast.  This  form  of  drill  hole  is  shown  in 
Fig.  7.  The  chamber  is  made  by  first  drilling  a 
hole  to  the  required  depth,  then  exploding  a  stick 

10 


Rock    Excavating    and    Blasting 


of  dynamite  at  the  bottom  of  the  drill  hole,  with 
little  or  no  tamping. 

This  operation  can  be  repeated  with  increased 
charges  until  a  chamber  of  the  right  size  is  ob- 
tained. A  caution  that  must  be  observed,  how- 
ever, in  this  method  of  working,  is  never  to  put 
the  powder  or  dynamite  in  the  chamber  until  the 
rock  has  cooled  to  its  normal  temperature.  Any 
attempt  to  charge  the  hole  immediately  after  a 
chambering  or  squibbing  blast  might  lead  to  a 
disastrous  explosion. 

In  large  operations,  like  the  blowing  up  of  Hell 
Gate,  New  York,  a  chamber  is  excavated  in  the 
rock  at  the  required  point, 
or  place,  and  a  tunnel  con- 
structed leading  into  the 
chamber,  so  it  can  be  charg- 
ed with  kegs  and  bags  of 
powder  or  other  explosives, 
ready  for  the  blast.  In 
ordinary  building  and 
engineering  construction, 
however,  the  drill  hole,  or 
drill  hole  and  chamber,  are 
about  all  that  will  be  neces- 
sary in  the  way  of  a  pocket 
to  hold  the  charge. 

Experience    shows    that  Fig.  7. 

drill  holes  having  diameters  A  "Chambered"  DHH  Hole, 
varying  from  three-quarters  of  an  inch  to   iy% 
inches  are  the  best  for  hard  rock,  if  charged  with 
the  strongest  high  explosives.     For  soft  rock,  on 

11 


Rock    Excavating    and    Blasting 

the  other  hand,  charges  of  weaker  explosives  are 
best,  and  they  should  be  in  drill  holes  l!/2  to  2i/£ 
inches  in  diameter. 

The  depth  of  drill  holes  will  generally  vary 
with  the  character  of  the  rock.  As  low  as  4  feet 
and  as  high  as  12  feet  are  not  extremes,  while 
depths  of  from  5  to  7  feet  would  probably  be 
considered  the  average  in  built-up  districts  where 
great  care  must  be  exercised. 

The  line  of  least  resistance  may  be  proportioned 
to  the  size  and  diameter  of  the  bore  hole,  accord- 
ing to  Table  I. 

TABLE  I. 
Size  of  Drill  Holes. 


Diameter  of  Drill  Hole 

\Y±  inches 

IM 

inches 

1%  inches 

f  Line  of  least  resistance  . 

.    3K  feet 

4 

feet 

5  feet 

\  Depth  of  drill  hole  .    .    . 

.    3K  feet 

4 

feet 

5  feet 

f  Line  of  least  resistance  .    , 

,    3%  feet 

5 

feet 

6  feet 

1  Depth  of  drill  hole  .    .    . 

.    5%  feet 

A  feet 

9  feet 

f  Line  of  least  resistance 

5     feet 

6 

feet 

7  feet 

I  Depth  of  drill  hole 

10     feet 

12 

feet 

14  feet 

According  to  this  table  shallow  bore  holes  are 
made  of  a  depth  equal  to  the  line  of  least  resist- 
ance; medium  depth  drill  holes  are  one  and  one- 
half  times  the  length  of  the  line  of  least  resist- 
ance; while  for  deep  holes,  10  feet  or  more,  the 
line  of  least  resistance  is  only  half  of  the  depth. 
In  open-cut  work  in  outlying  districts,  however, 
the  practice  is  generally  followed  of  drilling  the 
holes  one  and  one-half  times  the  length  of  the 
line  of  least  resistance.  For  instance,  in  work  on 

12 


Rock    Excavating    and    Blasting 


the  Chicago  Drainage  Canal  the  holes  were  drilled 
12  feet  deep  and  back  8  feet  from  the  face  of 
the  bench. 

EFFECT  OF  MULTIPLE  BLASTS.  —  A  greater  mass 
of  rock  can  be  dislodged  by  firing  two  or  more 
blasts  simultaneously  than  would  be  broken  down 
by  firing  the  same  shots  independently.  This 
greater  effectiveness  of  the  multiple  blasts  can 
be  seen  by  referring  to  Fig.  8.  If  the  blasts  a  and 


Fig.  8. 
Effect  of  Multiple  Blasts. 

b  were  touched  off  separately,  they  would  break 
out,  approximately,  the  amount  of  material  shown 
by  the  triangles  in  which  they  are  situated,  leav- 
ing the  inverted  triangular  mass  of  rock  c  intact ; 
while  if  these  two  charges  were  exploded  simul- 
taneously, they  would  blow  out  not  only  the  two 
triangular  masses  of  rock,  as  when  exploded 

13 


Rock    Excavating    and    Blasting 


separately,  but  they  would  dislodge  the  mass  of 
rock  represented  by  c  as  well. 

In  order  to  get  the  maximum  results  in  the  case 
of  multiple  blasts,  the  drill  holes  must  be  approxi- 
mately right,  or  right  if  possible.  In  the  case 
represented  by  Fig.  8  the  distance  between  the 
drill  holes  a  and  b  should  not  be  more  than  twice 
the  distance  they  are  back  from  the  face  of  the 
rock.  Naturally  the  distance  would  have  to  be 
varied  to  suit  the  character  of  the  rock,  being 
less  in  soft  than  in  hard  materials.  In  average 
strong  rock  the  holes  would  be  spaced  from  one 
and  one-half  to  two  times  the  distance  back  from 
the  free  face;  for  moderately  strong  rock  from 
one  to  one  and  one-half  times,  and  for  weak  rock 
the  distance  apart  should  not  exceed  the  line  of 
least  resistance.  Unfortunately,  there  is  no  mid- 
dle ground  between  theory  and  practice  in  the 
formulation  of  rules  as  to  the  form  of  cavity  and 
amount  of  material  dislodged  by  a  shot  or  multi- 
plicity of  shots;  consequently,  the  quantities 
given  can  only  be  approximate,  and  used  compar- 
atively as  a  guide.  Experience,  which  comes  only 
with  time,  is  the  only  safe  guide.  An  experienced 
quarryman  or  miner  will  study  the  character  of 
the  rock,  so  as  to  take  advantage  of  slip,  cleavage 
and  dip  of  the  rock,  and  be  able  to  place  his  holes 
at  such  angles  as  to  get  the  maximum  effects  and 
avoid  blow-out  shots. 

In  working  on  hard  rock,  it  is  well,  when  possi- 
ble, to  get  hard-rock  quarrymen  or  workmen  who 
have  had  experience  on  hard  rock;  while  for 

14 


Rock    Excavating    and    Blasting 


soft  rock,  workmen  with  experience  on  soft  rock 
are  to  be  preferred.  However,  the  superintend- 
ent must  often  work  with  the  labor  available,  and 
it  is  then  his  knowledge  of  rock  excavating  will 
be  invaluable. 

The  effect  of  multiple  blasts  is  still  further 
shown  in  Fig.  9.  In  this  example  three  holes 
are  drilled  close  together,  and  each  charged  with 
a  shot  that  if  fired  separately  would  not  break 


-  -.  -*-- IT    !! 


Fig.  9. 
Rock  Removed  by  Multiple  Biast. 


down  the  wall  of  rock  between  it  and  the  free 
vertical  face.  By  firing  three  charges  together, 
however,  all  that  mass  of  rock  bounded  by  the 
lines  will  be  displaced.  This  method  of  blasting 
will  be  found  useful  in  many  cases,  and  by  means 
of  it  greater  masses  of  rock  can  be  removed  with 
smaller  drill  holes  than  would  be  possible  were 
it  not  for  the  combined  effect  of  the  several 
charges.  To  secure  the  effect  of  a  multiple  blast 

IS 


Rock    Excavating    and    Blasting       (%^ffii) 

however,  the  charges  must  all  be  fired  simultan- 
eously, not  one  after  the  other  in  close  succession. 
When  explosions  follow  one  another,  even  with 
but  a  fraction  of  a  second  between  blasts,  the 
effect  is  lost,  for  the  blow  of  an  explosion  is  almost 
instantaneous.  After  the  first  shock  the  rock  be- 
comes shattered  sufficiently  to  reduce  the  pressure, 
and  with  shots  following  one  another,  the  force 
of  one  blast  is  liable  to  be  spent  before  another 
comes  into  action.  Electric  firing  of  blasts  is  the 
only  way  in  which  the  charges  can  be  exploded 
simultaneously.  No  matter  how  experienced  and 
careful  a  rock-man  may  be,  he  cannot  time  fuses 
so  the  charges  will  all  fire  together.  Differences 
of  a  little  in  length ;  slower  or  quicker  burning  of 
some  of  the  fuses,  or  delay  of  some  of  the  fuses 
in  taking  fire  will  all  contribute  more  or  less  to 
the  scattering  of  shots. 


16 


CHAPTER  II. 


SINKING  SHAFTS  THROUGH  ROCK. 


RILL  HOLES  IN  SHAFT  SINKING. — 
There  is  considerable  latitude  al- 
lowed the  quarryman  in  the  placing 
of  drill  holes  for  shaft  sinking  and 
tunnel  driving,  but  whatever  their 
arrangement,  they  all  are  based  on  the  principle 
that  there  is  but  one  free  face  in  that  class  of 
work,  and  to  get  the  best  results  two  faces  must 
be  exposed.  In  order  to  get  two  free  faces,  key 
holes,  or  cut  holes,  are  drilled  and  fired  in  order 
to  blow  out  a  portion  of  the  rock,  and  the  work- 
men then  arrange  the  drill  holes  to  take  advantage 
of  this  cavity.  It  is  not  necessary  to  actually 
drill  and  blast  those  cut  holes  first,  for  the  effect 
of  the  blast  being  known,  the  key  holes  can  be 
drilled  at  the  time  all  the  other  holes  are  drilled, 
then  they  can  be  fired  first  to  make  a  second  free 
face  for  the  other  blasts. 

The  location  of  drill  holes  for  shaft  sinking  and 
tunnel  driving  is  practically  the  same.  The  key 
holes  may  be  arranged  in  a  circular  form  to  take 
out  a  cone  of  rock,  and  the  drill  holes  arranged 

17 


Rock    Excavating    and    Blasting 


in  concentric  circles  outside  of  this  cone,  or  the 
key  holes  may  be  arranged  in  straight  lines  to 
take  out  a  wedge-shaped  core  of  rock.  One 
method  of  arranging  drill  holes  for  shaft  sinking 
through  a  white  limestone  is  shown  in  Fig.  10. 
The  approximate  dimensions  are  given  on  this 


Fig.  10. 
Arrangement  of  Drill  Holes  in   Shaft  Sinking. 

illustration  as  a  guide  to  the  judgment  in  arrang- 
ing drill  holes  and  spacing  them  in  similar  work. 
The  rows  of  drill  holes  are  numbered  1,  2,  3  and 
4  for  convenience  in  reference.  The  depth  of  the 
cut  was  6  feet,  and  the  dimensions  of  the  shaft 

18 


Rock    Excavating    and    Blasting 


20  by  20  feet,  one-half  only  of  which  is  shown. 
In  sinking  a  shaft  of  this  kind,  the  holes  would 
all  be  drilled  in  one  shift.  The  rows  of  holes 
2,  3  and  4  would  then  be  protected  so  they  would 
not  fill  with  dirt;  the  double  rows  of  holes  1-1 
be  charged  with  the  explosives,  and  the  charges 
fired  simultaneously.  This  would  cut  or  blow  out 
its  wedge-shaped  mass  of  rock  bounded  by  the 
lines  of  drill  holes  at  the  sides  and  the  free  face 
on  the  top.  The  removal  of  this  wedge  of  rock 
exposes  two  free  faces  on  each  side  of  the  cavity, 
and  the  double  row  of  holes  2-2  would  then  be 
charged  and  fired.  After  the  rock  from  this  blast 
had  been  cleared  away  the  double  rows  of  holes 
3-3  would  in  like  manner  be  charged  and  fired, 
and  after  clearing  out  the  rock  dislodged  by  the 
blast  the  squaring-up  rows  of  holes  4-4  would 
be  fired. 

After  the  first  level  of  the  shaft  has  been  blasted 
and  the  rock  removed,  the  experience  gained 
ought  to  show  whether  a  different  arrangement 
of  the  drill  holes  or  a  heavier  or  weaker  charge 
of  explosive  were  necessary. 

The  object  is,  of  course,  to  remove  all  the  rock 
necessary,  so  holes  will  not  have  to  be  hand-drilled 
for  squaring-up  purposes,  and  at  the  same  time 
to  use  charges  of  explosive  of  only  sufficient 
strength  to  remove  the  rock  at  each  blast  without 
shattering  the  side  wails  of  the  shaft  or  blowing 
the  removed  material  to  atoms. 

It  will  be  noticed  that  the  squaring-up  drill 
holes,  4-4,  are  slanted  so  as  to  bring  them  a  little 

19 


Rock    Excavating    and    Blasting 


outside  of  the  plumb  line  of  the  shaft.  This  is 
because  the  drill  operator  cannot  place  his 
machine  close  enough  to  the  shaft  wall  to  drill  a 
truly  perpendicular  hole,  and,  in  order  to  take 


Fig.  U. 
Deep  Drill  Holes  for  Shaft  Sinking. 


out  enough  rock  so  as  not  to  necessitate  subse- 
quent cutting  and  blasting,  the  drill  hole  is  put 
in  at  a  slight  angle  to  bring  the  bottom  of  the 
charge  of  explosive  outside  of  the  plumb  line  of 

20 


Rock    Excavating    and    Blasting 


the  shaft,  or  the  side  line  of  the  tunnel,  as  the 
case  may  be. 

In  this  example  the  cut  is  a  shallow  one,  only  6 
feet  of  material  being  removed  for  each  cycle  of 
operations.  In  the  method  shown  in  Fig.  11, 
eleven  feet  of  the  same  material  can  be  removed 
by  one  cycle  of  operations.  In  working  accord- 
ing to  this  plan  of  shaft  sinking,  the  primary  rows 
of  cut-out  holes,  1-1,  are  drilled  as  in  the  preced- 
ing case,  but  reaching  to  a  depth  of  6  feet  only. 
Secondary  rows  of  cut-out  holes,  2-2,  are  then 
drilled,  meeting  at  a  depth  of  11  feet  from  the 
surface,  and  the  ordinary  rows  of  blast  holes,  3-3 
and  4-4,  together  with  the  squaring-up  rows  of 
holes,  5-5,  are  next  drilled. 

After  protecting  all  the  other  holes,  the  double 
row  of  cut-out  holes,  1-1,  are  charged,  fired  and 
the  rock  cleared  away. 

Having  two  free  faces  for  part  of  the  depth, 
the  double  row  of  secondary  cut-out  holes,  2-2, 
are  then  charged  and  fired  and  the  rock  cleared 
away. 

There  are  now  two  free  faces  for  the  remain- 
ing blasts  to  operate  on,  and  the  rows  of  drill 
holes  are  charged  and  fired  in  their  consecutive 
orders,  3-3,  4-4  and  5-5,  each  battery  of  charges 
in  the  like  double  rows  being  fired  simultaneously 
to  get  the  maximum  effect  of  the  shots.  In  shaft 
sinking  there  are  two  operations  besides  the  drill- 
ing and  blasting  which  must  be  considered.  As 
the  shaft  goes  deeper  and  deeper,  more  and  more 
water  will  seep  into  it,  just  as  it  would  in  a  well, 

21 


Rock    Excavating    and    Blasting 


and  provision  must  be  made  to  pump  out  this 
water  as  fast  as  it  accumulates.  Sometimes,  in 
high  places,  this  is  a  simple  matter,  while  in  other 
localities  in  low-lying  land  pumps  must  be  kept 
constantly  at  work  to  maintain  the  shaft  in  work- 
ing condition. 

A  hoist  must  be  rigged  up,  too,  with  which  to 
remove  the  rock  loosened  by  blasting.  Ordinarily 
there  is  but  little  danger  of  rock  from  the  walls 
falling  into  the  shaft  on  top  of  the  workmen,  pro- 
vided they  inspect  the  walls  closely  as  the  shaft  is 
deepened,  and  see  that  no  loose  pieces  of  stone  are 
left  hanging  to  the  walls,  to  be  jarred  out  of  place 
later  on. 


22 


CHAPTER  III. 


TUNNEL  DRIVING. 


RILL  HOLES  FOR  TUNNEL  DRIVING  IN 
SOFT  ROCK.  —  In  driving  tunnels 
about  the  same  system  of  drilling 
would  be  followed  as  for  shaft  sink- 
ing. The  methods  previously  ex- 
plained would  be  found  quite  satisfactory  for  a 
medium  sized  tunnel,  while  that  shown  in  Fig  12 
may  be  successfully  followed  for  small  tunnel 
driving  in  medium  hard  rock.  It  will  be  noticed 
in  this  system  of  drilling  that  three  drill  holes 
are  bored  in  a  circle,  or  so  as  to  form  a  triangle, 
and  the  other  holes  are  drilled  around  the  edge 
of  the  tunnel  close  to  the  sides.  The  center  tri- 
angle holes  are  drilled  toward  a  central  point 
about  6  feet  below  the  face  of  the  rock.  These 
three  holes  form  the  key  holes,  or  cut  holes, 
which  are  to  be  charged  and  fired  first,  the  other 
holes  then  being  charged  after  the  rock  has  been 
cleared  away,  and  the  charges  fired  simultane- 
ously. 

In  this  illustration,  on  account  of  the  small  size 
of  the  tunnel,  only  one  row  of  holes  is  drilled  out- 

23 


Rock    Excavatiid    Blasting 


side  of  the  cut  holes.  In  a  large  tunnel,  however, 
if  this  method  were  used,  two,  three  or  more  rows 
of  holes  would  be  drilled,  according  to  the  size 
of  the  operation  and  the  quality  of  the  rock. 

In  one  respect,  the  drill  holes  for  tunnel  work 
differ  slightly  from  the  system  of  drill  holes  used 
for  shaft  sinking.  In  the  case  of  tunnel  driving 


Fig.  12. 
Rock   Drilling  in   Small   Tunnel.     Soft   Rock. 

in  soft  or  shaly  materials,  the  drill  holes  are  not 
spaced  uniformly.  This  can  be  easily  seen  by  re- 
ferring to  Fig.  13,  which  is  a  diagram  showing 
the  location  and  surface  arrangement  of  drill 
holes  in  the  tunnel  illustrated  in  Fig.  12.  It  will 
be  observed  that  there  are  more  drill  holes  in  the 
bottom  half  of  the  diagram  than  in  the  top  half. 
Beginning  with  the  bottom  row,  there  are  three 

24 


Rock    Excavating    and    Blasting 

holes,  as  against  two  holes  in  the  top  row;  while 
the  second  row  from  the  bottom  has  four  holes  to 
three  holes  in  the  third  row.  The  reason  for  this 
is,  gravity  helps  to  bring  down  the  mass  of  rock 
from  the  roof  of  the  tunnel,  wrhile  the  rock  from 
the  bottom  of  the  tunnel  must  be  shattered  and 


Fig.  13. 
Diagram  of  Drill  Holes  in  Tunnel.    Soft  Rock. 

torn  away  in  spite  of  the  resistance  it  encounters 
and  the  weight  of  rock  above.  The  moment  soft 
rock  or  shaly  material  is  shattered  along  the  roof 
of  the  tunnel,  it  falls  by  its  own  weight,  therefore 
a  greater  amount  of  rock  can  be  torn  loose  by  a 
blast  than  if  in  the  bottom  of  the  tunnel,  where 

25 


Rock    Excavating    and    Blasting 


the  shot  has  not  only  to  rend  the  rock,  but  lift 
it  as  well. 

Further,  the  roof  of  the  tunnel  does  not  want 
to  be  shattered  too  much  by  numerous  or  large 
blasts,  or  masses  of  rock  might  be  loosened  and 
hang  suspended  without  being  noticed,  until  a 


Fig.  14. 
Drill  Holes  for  Small  Tunnel  in  Hard  Rock. 

subsequent  jar  detaches  it  and  allows  it  to  fall 
to  the  floor,  endangering  the  lives  of  the  work- 
men. For  these  reasons,  it  is  better  to  use  only 
enough  explosive  and  as  many  drill  holes  in  the 
upper  half  of  the  tunnel  as  will  remove  the  right 
amount  of  rock,  without  subsequent  hand  drilling. 

26 


Rock    Excavating    and    Blasting 


In  blasting,  according  to  this  system,  the  holes 
a  a  a  would  first  be  charged  and  fired.  Next  the 
holes  b  b,  and  finally  the  finishing  holes  c  c.  Some 
quarrymen  fill  the  holes  b  b  and  c  c  simultane- 
ously. It  is  better  though  to  fire  holes  b  b  first 
and  remove  the  rock  before  charging. 

In  drilling  the  cut  holes,  the  practice  differs 
among  quarrymen.  Some  rockmen  drill  the  holes 
so  they  will  not  meet,  with  the  view  of  making 
a  wide  end  to  the  cavity  broken  out  by  the  blast. 
Other  quarrymen,  on  the  other  hand,  drill  the  cut- 
out holes  so  they  meet  at  a  common  point.  Where 
drill  holes  meet  in  that  manner  they  form  an  en- 
larged chamber  in  which  a  large  quantity  of  pow- 
der can  be  placed,  consequently,  a  more  effective 
blast  can  be  had  than  from  single  drill  holes. 

DRILL  HOLES  FOR  TUNNELING  IN  HARD  ROCK.— 
A  system  of  drilling  for  tunneling  through  hard 
rock  is  shown  in  Fig.  14.  This  system  does  not 
differ  much  from  the  one  for  soft  rock  and  shaly 
formations,  other  than  having  a  greater  number 
of  drill  holes.  In  this  case  there  are,  first,  four 
cut-out  holes,  1-1,  to  blast  out  a  cone-shaped  cav- 
ity. Next,  there  are  four  enlarging  holes,  2-2,  for 
the  purpose  of  enlarging  the  cavity  and  giving  a 
larger  free  surface  to  work  upon.  Last  comes 
the  row  of  holes  around  the  sides  of  the  tunnel. 
The  four  holes  numbered  1  would  be  charged  and 
fired  at  one  time.  After  the  rock  removed  by  the 
blast  had  been  cleared  away,  the  holes  numbered 
2  would  be  charged  and  fired.  Next,  after  having 

27 


Rock    Excavating    and    Blasting 


cleared  away  the  loose  rock,  the  drill  holes  num- 
bered 3  along  the  roof  and  sides  of  the  tunnel 
would  be  charged  and  fired,  and  finally  the  row 
of  drill  holes  along  the  floor  of  the  tunnel  would 
be  charged  and  fired.  The  drill  holes  3  and  4  are 
fired  simultaneously  by  some  quarrymen,  but  bet- 
ter results  will  be  obtained  by  firing  the  number 
3  holes  and  follow  with  the  number  4. 

The  foregoing  illustrations  of  drilling  for  blast- 
ing cannot  be  accepted  as  the  proper  system  to 
use  in  all  cases,  but  only  as  fair  averages,  show- 
ing the  principles  of  rock  excavation.  Differ- 
ences in  the  hardness  of  rock,  veins  of  harder  or 
softer  material  crossing  the  shaft  or  tunnel,  fis- 
sures or  faults  in  the  strata  would  all  necessitate 
changes  from  the  order  shown,  and  the  experi- 
ence of  the  rockmen  must  be  the  guide  in  such 
cases.  No  rules  can  be  given  that  will  be  applic- 
able to  every  case,  and  no  illustrations  can  pos- 
sibly show  the  right  thing  to  do  every  time.  At 
best,  the  principles  are  all  that  can  be  successfully 
taught  in  any  line.  Experience  must  improve 
that  knowledge  to  make  it  of  practical  value.  For 
example,  in  extremely  large  tunnel  work  the  up- 
per part  of  the  tunnel  would  be  driven  as  explain- 
ed in  the  foregoing  paragraphs,  and  the  lower 
portion  worked  in  benches  similar  to  open-cut  or 
quarry  work. 

DRILLING  NEAR  FAULTS  OR  FISSURES. — A  meth- 
od of  drilling  rock  in  a  shaft  or  tunnel  where  there 
is  a  fault,  fissure,  slip  in  the  rock  or  a  semi-free 

28 


Rock    Excavating    and    Blasting 


face  of  any  kind  is  shown  in  Fig.  15.  The  usual 
cut-holes  in  the  center  of  the  face  are  omitted, 
and  instead  side  cuts,  or  drillings,  are  made  in 
the  heading,  in  the  direction  of  the  slope  or  fis- 
sure. Care  must  be  exercised,  however,  not  to 


Fig.  15. 
Drill  Holes  Near  Fissures  or  Faults. 

drill  through  the  rock  into  the  fissure  or  too  close 
to  its  face,  or  when  the  blast  is  touched  off  a  part 
or  most  of  its  force,  depending  upon  the  size  and 
openness  of  the  rock,  will  be  expended  without 
doing  any  good.  In  this  method  of  drilling,  two 
holes,  1-1,  are  the  cut-holes.  They  are  not  ex- 

29 


(g^jfr      Rock    Excavating    and    Blasting       &/j^) 

tended  clear  down  to  the  bottom  of  the  cut, 
but  only  a  sufficient  distance  to  dislodge  a  large 
enough  wedge  of  rock  to  give  a  large  free  sur- 
face for  the  subsequent  blasts  to  work  upon.  The 
rest  of  the  drill  holes  are  carried  the  full  depth 
of  the  cut,  which,  in  this  method,  would  perhaps 
not  exceed  4  feet,  at  about  the  angles  shown  in 
the  illustration.  In  blasting  they  would  be  fired 
in  volleys,  according  to  the  way  they  are  num- 
bered. 

In  the  first  volley  the  charges  in  holes  1-1  would 
be  fired.  After  the  rock  had  been  cleared  away, 
holes  2-2  would  be  charged,  and  fired  simultane- 
ously. When  the  rock  from  that  blast  had  been 
removed,  holes  3-3  would  be  charged  and  fired; 
and,  finally,  the  squaring  holes,  4-4,  would  be 
loaded  and  fired. 

In  some  rock  formations  a  thin  seam  of  soft  or 
rotten  stone,  or  soft  coal,  from  4  inches  to  12 
inches  thick,  is  encountered.  Where  such  is  the 
case,  the  soft  material  can  be  cut  out  with  a  pick, 
blown  out  with  a  small  shot  or  otherwise  removed 
for  a  distance  of  4  to  6  feet,  thus  forming  an  un- 
dercut which  gives  a  large,  free  surface  and  dou- 
ble face  to  work  upon.  Under  such  conditions 
cut  holes  can  be  omitted,  and  the  shot  placed  in 
the  best  position  to  bring  down  the  greatest 
amount  of  material,  according  to  principles  prev- 
iously explained  for  blasting  where  two  free  faces 
are  exposed. 

DRIVING  LARGE  TUNNELS. — In  Fig.  16  is  shown 
the  way  a  large  tunnel  is  driven,  the  work  being 

30 


Rock    E:x          ating    and    Blasting 


31 


Rock    Excavating    and    Blasting 


done  in  two  operations,  driving  the  heading  and 
blasting  the  bench.  The  heading  is  driven  by 
drilling  the  breast  of  the  rock  and  blasting  it  the 
same  as  for  a  small  tunnel.  Indeed,  this  part  of 
the  operation  may  be  considered  as  driving  a  small 
tunnel.  This  takes  out  only  part  of  the  material 
that  must  be  removed,  however,  and  the  second 
operation  which  is  in  the  nature  of  enlarging  the 
opening  first  made,  consists  of  blasting  out  the 
bench,  a  process  which  is  carried  on  in  much  the 
same  manner  as  would  be  done  in  open-cut  work, 
only  smaller  charges  of  explosive  are  used. 

In  order  to  condense  the  principle  features  of 
tunnel  driving  into  a  one-page  illustration,  the 
drawing  is  made  out  of  proportion.  In  the  first 
place,  the  heading  and  bench  would  not  be  so 
close  together.  In  very  large  operations  the 
heading  and  bench  are  so  far  apart  that  working 
on  one  does  not  interfere  with  work  on  the  other. 
Again,  the  bench  is  generally  deeper  in  propor- 
tion than  the  heading,  a  condition  which  is  re- 
versed in  the  illustration. 

In  large  tunnel  operations,  instead  of  one  rock- 
man  operating  a  drill  in  the  heading,  two,  and 
sometimes  three  work  simultaneously  with  power 
drills  mounted  on  mining  columns ;  and  instead  of 
starting  operations  at  one  side  of  a  hill  or  moun- 
tain and  driving  through  to  the  opposite  side, 
the  tunnel  is  started  at  both  ends  at  the  same 
time,  and  the  workmen  meet  with  the  tunnel  in 
the  middle  of  the  mound  they  are  driving  through. 

Back  of  the  bench  is  the  "muck-heap,"  as  the 

32 


Rock    Excavating    and    Blasting 


material  loosened  by  the  blast  is  called,  and  the 
workmen  engaged  in  removing  the  "muck"  from 
the  working  are  known  as  "muckers." 

No  support  or  lining  is  shown  in  the  illustra- 
tion, as  the  operations  of  rock  blasting  and  ex- 
cavating only  are  intended  to  be  shown.  How- 
ever, as  the  heading  progresses,  props  or  posts 
are  put  up  to  support  the  roof  of  the  tunnel,  and 
prevent  rock  loosened  by  the  blasting  from  crush- 
ing down  on  the  workmen.  After  the  bench  is 
blasted,  the  tunnel  is  lined,  either  with  temporary 
or  permanent  lining;  and  when  permanently 
lined,  the  space  between  the  masonry  lining  and 
the  rock  walls  of  the  tunnel  is  flushed  full  of  con- 
crete or  grout.  During  the  driving  of  a  tunnel, 
particularly  through  wet  or  seamy  ground,  pro- 
vision must  be  made  to  take  care  of  the  seepage 
which  in  some  cases  is  considerable.  Indeed,  in 
limestone  localities,  underground  streams  are 
often  encountered  when  driving  tunnels  below  the 
hydraulic  gradient. 

Between  the  dangers  of  falling  roof  ;  of  prema- 
ture blasts;  accidents  to  the  storage  magazine; 
gas  ;  fumes  from  the  explosives  and  poor  air  gen- 
erally of  the  underground  workings,  it  requires 
the  most  watchful  care  on  the  part  of  those  in 
charge  to  prevent  damage,  injury  or  death  to 
those  in  their  care.  As  soon  as  the  heading  is 
driven  a  short  distance,  the  roof  should  be  held 
up  with  good  stout  props.  Then,  as  the  bench 
work  follows  the  heading  and  props  have  to  be 
removed  to  make  way  for-  the  workmen,  the  roof 

33 


Rock    Excavating    and    Blasting 


back  of  the  bench  must  be  supported  until  the 
lining,  temporary  or  permanent,  is  in  place. 

The  removing  of  the  rock  blasted  out  of  the 
tunnel  is  no  small  task,  and  a  clear  runway  must 
be  maintained  for  the  tracks  and  the  muck  cars 
which  take  the  rock  out  of  the  tunnel.  In  the 
case  of  large  tunnels  driven  in  mountains  or  hills, 
the  muck  is  carted  out  on  dump  cars,  and  de- 
posited in  muck  heaps  at  convenient  points.  In 
driving  tunnels  under  the  streets  of  cities,  how- 
ever, the  disposal  of  the  rock  removed  sometimes 
is  a  problem  in  itself.  Some  of  it  can  be  disposed 
of  for  building  purposes,  but  getting  it  to  the  sur- 
face and  carting  it  away  without  interfering  too 
much  with  the  ordinary  traffic  is  one  of  the  prob- 
lems that  must  be  considered. 


34 


PART  II. 


ROCK-DRILLING  TOOLS  AND 
MACHINERY. 

sft?        ty 
CHAPTER  IV. 

HAND  AND  AIR  DRILLS. 


OCK  DRILL  ON  TRIPOD.  —  Hand  drill- 
ing of  rock,  with  sledge  and  chisel 
bar  or  drill  steel,  of  course  every- 
body is  familiar  with,  but  under 
present-day  conditions  economy  of 
time  and  labor  will  not  tolerate  that  old-time 
method,  which  has  been  supplanted,  so  far  as 
large  operations  are  concerned,  by  rock  drills 
operated  by  power. 

The  commonest  types  of  power  drills,  and  the 
ones  most  extensively  used,  in  general  engineering 
work  are  the  reciprocating,  or  striking,  machines, 
operated  either  by  steam  or  by  compressed  air. 
A  rock  drill  of  this  type,  mounted  on  an  adjust- 
able tripod  is  shown  in  Fig.  17.  The  legs  of 
the  tripod  on  which  this  machine  is  mounted  are 

35 


(^^jfr      Rock    Excavating    and    Blasting       (tffi& 

provided  with  universal  joints,  so  they  can  be 
adjusted  to  the  uneven  surface  common  to  all 
operations,  and  are  weighted  with  heavy  castings 
to  hold  the  machine  firmly  in  place,  and  prevent 


Fig.  17. 

Rock  Drill  on  Tripod. 
36 


Rock    Excavating    and    Blasting 


it  being  raised  from  the  surface  every  time  the 
drill  strikes  the  rock  at  the  bottom  of  the  hole. 

Rock  drills  are  made  in  various  sizes,  with 
lengths  of  stroke  ranging  all  the  way  from  4 
inches  to  8  inches,  and  that  will  drill  holes  of 
diameters  ranging  from  %-inch  up  to  6  inches. 

Further,  a  machine  of  this  type  will  drill  holes 
from  1  inch  to  32  feet  in  depth,  while  larger  ma- 
chines of  similar  type  have  been  successfully  and 
economically  used  to  drill  holes  50  to  60  feet  deep, 
and  ranging  in  size  from  6  inches  at  the  top  to 
?  inches  at  the  bottom. 

In  drilling  with  a  power  drill  only  a  certain 
depth  of  hole  can  be  drilled,  depending  on  the 
length  of  feed  of  the  machine,  when  the  feed  must 
be  readjusted,  a  longer  drill  fitted  in  the  chuck, 
and  the  hole  extended  down  as  far  as  the  feed 
will  permit,  when  the  operation  of  readjusting 
must  be  repeated  until  the  hole  is  carried  to  its 
final  depth.  Twelve  inches  is  the  length  of  feed, 
or  depth  that  can  be  drilled  without  changing 
steels,  for  the  smallest  machines,  and  from  that 
minimum  the  length  of  feed  is  gradually  increased 
in  the  various  sizes  until  the  maximum,  30  inches, 
is  reached. 

In  holes  that  are  drilled  to  a  considerable  depth 
different  sizes  of  steels  are  used,  the  diameter  be- 
coming smaller  as  the  holes  grow  deeper,  so  there 
will  be  no  binding  of  the  drill  steel  in  the  holes. 
The  length  of  stroke,  length  of  feed,  depth  of 
hole  a  machine  will  drill,  diameter  of  hole,  num- 
ber of  drill  steels  required  to  drill  the  maximum 

37 


^^S       Rock    Excavating 

and    Blasting        Q^l 

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38 

Rock    Excavating    and    Blasting 


depth,  as  well  as  a  lot  of  other  information  re- 
garding these  drills,  can  be  found  in  Table  II. 

The  drill  steel  is  kept  well  down  in  the  hole  it 
has  formed  by  means  of  the  feed  screw  shown  at 
the  top  in  the  illustration,  and  the  steam  or  air 
supply  may  be  attached  either  to  the  right  or  left 
side  of  the  machine.  In  this  case  it  is  connected 
to  the  right  side  by  means  of  a  flexible  tubing 
wound  with  wire,  and  the  supply  of  steam  or  air 
is  controlled  by  a  stop  cock  convenient  to  the  op- 
erator's hand.  In  ordering  rock  drills  the  order 
should  state  whether  steam  or  compressed  air  is 
to  be  used.  Drills  are  always  supplied  with  pack- 
ings for  steam  unless  air  is  specified  as  the  motive 
power. 

ROCK  DRILL  ON  QUARRY  BAR. — The  rock  drill 
on  quarry  bar  is  practically  the  same  as  the  ordi- 
nary rock  drill,  the  principal  difference  being  the 
mounting.  For  plug  and  feather  work  in  quar- 
ries, channeling  or  any  other  kind  of  drilling 
where  it  is  necessary  to  have  the  holes  in  a  line 
and  parallel  with  one  another,  the  quarry  bar  is 
used.  A  mounting  of  this  description  may  be 
seen  in  Fig.  18.  Once  this  bar  has  been  properly 
set  up  and  secured  in  place,  the  drill  can  be  moved 
along  from  place  to  place,  drilling  holes  as  close 
together  or  as  wide  apart  as  the  operator  pleases. 
Holes  can  be  drilled  so  close  together,  in  fact, 
that  they  form  almost  a  continuous  channel,  and 
can  be  used  for  channeling  by  breaking  out  the 
core  or  partition  between  the  holes  by  means  of  a 
special  broaching  bit.  Large  blocks  of  stone  can 

39 


Rock    Excavating    and    Blasting 


40 


Rock    Excavating    and    Blasting 


likewise  be  taken  out  of  the  quarry,  without 
breaking  or  shattering,  by  the  plug  and  feather 
method  —  that  is,  a  series  of  holes  are  drilled  in  a 
row  and  a  break  is  made  along  the  line  of  holes 
by  means  of  wedges. 

Quarry  bars  of  this  type  are  made  in  lengths 
of  8,  10  and  12  feet,  and  the  carriage  is  so  con- 
structed that  it  can  be  easily  and  quickly  moved 
along  the  bar,  thus  changing  the  position  of  the 
drill  without  loss  of  time,  as  would  occur  with 
the  tripod  mounting.  The  quarry  bar  is  fre- 
quently used  for  channeling  in  engineering  and 
architectural  works  where  the  nature  of  the  rock 
prevents  the  use  of  channeling  machines. 

ROCK  DRILL  ON  MINING  COLUMN.  —  Both  the 
drill  mounted  on  the  tripod  and  that  on  the  quarry 
bar  are  designed  for  cutting  or  drilling  holes 
downward,  either  vertically  or  at  slight  angles 
from  the  vertical.  In  driving  tunnels,  mining 
and  similar  works  it  is  necessary  to  have  a  drill 
that  can  be  pointed  in  any  direction,  up  or  down, 
or  straight  overhead.  In  the  mining  column 
shown  in  Fig.  .19  we  have  such  a  machine.  These 
columns  are  made  in  several  lengths,  to  suit  dif- 
ferent heights  of  drifts,  and  are  secured  in  place 
by  tightening  the  jack  screws  at  the  bottom  to 
jam  the  top  of  the  column  tight  against  the  roof 
of  the  tunnel  if  set  upright,  or  against  the  side 
of  the  working  if  set  on  side.  The  usual  length 
of  column  is  6  feet,  with  the  jack  screws  drawn  in. 

The  drill  is  perfectly  adjustable  when  mounted 
on  one  of  these  columns,  as  it  may  be  swung  tc 

41 


Rock    Excavating    and    Blasting 


1 


Rock    Excavating    and    Blasting 


drill  in  any  direction.  It  may  also  be  moved  up 
or  down  on  the  column,  and  as  a  further  adjust- 
ment may  be  revolved  in  the  saddle.  In  fact, 
there  is  no  position  in  which  the  drill  cannot  be 
set  up. 

In  using  a  column,  wood  blocking  should  al- 
ways be  placed  at  the  ends  to  give  an  even  bind- 
ing surface. 

Rock  drills  are  operated  by  compressed  air  for 
all  mine  and  tunnel  work,  and  air  is  also  replacing 
steam  to  a  constantly  increasing  extent  for  quar- 
rying and  other  work  above  ground.  The  mount- 
ing principally  employed  for  the  former  purposes 
is  the  mining  column  or  shaft  bar,  while  tripods, 
quarry  bars,  etc.,  are  used  on  the  latter  work. 
The  operation  of  columns  is,  therefore,  described 
using  air,  and  the  operation  of  tripods  with  the 
instructions  for  running  when  using  steam.  In- 
structions regarding  the  setting  up  and  operat- 
ing of  steam  and  compressed-air  drills,  furnished 
by  the  manufacturers  from  their  extensive  expe- 
rience, are  given  in  the  following  chapter.  In 
operating  a  rock  drill,  no  matter  what  its  mount- 
ing may  be,  it  is  necessary  to  so  handle  the  ma- 
chine that  the  drill  steel  will  not  bind  or  stick  in 
the  drill  hole.  There  is  not  so  much  danger  of 
this  in  drill  holes  which  point  down,  for  the  rota- 
tion of  the  drill  steel  will  keep  the  hole  large 
enough  and  in  sufficient  alignment,  particularly 
when  the  drill  steel  is  properly  made  with  the 
right  gauge  of  wings  or  vanes.  As  the  hole  to  be 
drilled  varies  from  the  vertical  to  the  overhead 

43 


Rock    Excavating    and    Blasting 


angle,  however,  the  liability  of  the  drill  steel  stick- 
ing increases.  This  is  because  the  dust  and  chip- 
pings  fall  to  the  lower  side  of  the  drill  hole,  there- 
by protecting  the  lower  side,  and  forcing  the  drill 
steel  against  the  upper  part  of  the  hole  all  the 
time.  The  result  of  this  is,  the  hole  describes 
more  or  less  of  an  arc  as  the  depth  increases,  and 
to  compensate  for  this  upward  movement,  the 
drill  must  be  lowered  on  its  mountings  from  time 
to  time. 

The  inclination  or  tendency  of  a  drill  steel  to 
curve  the  hole  upward  can  be  checked  to  a  great 
extent  by  keeping  the  hole  free  from  dust  and 
chippings.  In  horizontal  holes  and  those  with 
but  a  slight  upward  tilt,  a  wire  with  hook  on  end 
will  enable  the  operator  to  rake  the  cuttings  out. 


44 


CHAPTER  V. 


OPERATING  DRILLING  MACHINES. 


UNNING  WITH  COMPRESSED  Am  — 
SETTING  UP  AND  STARTING.—  In  set- 
ting up  a  mining  column  or  shaft 
bar  it  is  well  to  set  the  jackscrews 
on  a  solid  block  of  hardwood.  In 
drifting  always  set  the  jackscrews  parallel  with 
the  direction  of  the  tunnel.  Run  the  jackscrews 
back  as  far  as  possible,  set  the  column  or  bar  in 
position,  and  place  blocks  or  wedges  tightly  be- 
tween the  top  plate  and  the  rock.  Draw  up  on 
the  jackscrews,  and  as  the  drill  is  started  keep 
tightening  the  screws  until  the  column  or  bar  is 
secure.  In  a  drift  or  tunnel  the  columns  should 
be  as  long  as  possible,  so  that  resetting  of  the  col- 
umn when  the  bottom  holes  are  reached  may  be 
avoided.  The  mounting  being  in  place,  fasten  the 
machine  rigidly  to  it.  The  connections  to  the 
mounting  should  always  be  firm  and  tight,  as  the 
slipping  of  a  clamp  or  saddle  will  make  the  drill 
"fitcher,"  or  stick,  frequently  causing  the  loss  of  a 
hole.  Always  blow  out  the  hose  before  connect- 

45 


Rock    Excavating    and    Blasting 


ing  it  to  the  drill.  Before  starting,  the  rock  should 
be  squared  off  where  the  hole  is  to  be  put. 

DRY  HOLES. — Start  the  drill  slowly  and  on  a 
short  stroke.  In  drilling  dry  holes,  or  those  at  a 
small  angle  above  the  horizontal,  it  should  be 
remembered  that  such  holes  have  a  tendency  to 
turn  upward,  due  to  the  accumulation  of  cuttings 
on  the  lower  side,  which  tends  to  raise  the  drill 
bit  at  each  stroke.  It  is  well  to  start  the  hole  a 
little  below  the  desired  angle,  and  it  is  often 
necessary  to  lower  the  drill  on  the  column  in 
order  to  keep  the  steel  from  binding  in  the  top 
of  the  hole.  Care  should  be  taken  that  the 
cuttings  are  continually  running  out  of  a  dry  hole 
while  drilling.  If  allowed  to  accumulate  in  the 
hole  they  tend  to  pack  behind  the  bit,  and  often 
cause  difficulty  and  loss  of  time  in  getting  the 
steel  out,  as  well  as  reducing  the  progress  of  the 
drilling.  The  flow  of  the  cuttings  in  a  flat  or 
horizontal  hole  may  be  assisted  by  means  of  a 
long  wire  picker.  If  the  cuttings  stop  running, 
close  the  throttle  until  the  drill  reciprocates  slow- 
ly, then  crank  the  drill  backwards  out  of  the  hole 
the  full  length  of  the  feed  screw.  This  clears 
away  the  cuttings  from  behind  the  bit,  leaving  the 
hole  free  for  further  drilling.  The  tendency  of 
cuttings  to  pack  in  the  hole  increases  in  damp 
ground,  and  especial  care  should  be  used  in  this 
case.  Steels  should  be  dry  when  inserted  in  the 
hole,  for  if  a  wet  steel  be  put  into  a  dry  hole  the 
dust  adheres  to  it  and  clogs  it. 

46 


Rock    Excavating    and    Blasting 


DOWN  HOLES.  —  In  drilling  down  holes  or  those 
at  any  angle  below  the  horizontal,  care 
should  be  used  to  feed  water  at  such  a 
rate  that  there  will  be  a  continual  dash 
of  mud  out  of  the  hole.  If  too  much 
water  is  used  the  hole  will  fill  up,  and 
the  dashing  will  be  prevented,  quickly 
resulting  in  a  clogged  or  mudded  hole. 
If  too  little  water  is  used  the  drill  wastes 
most  of  its  energy  in  stirring  up  the 
heavy  mud  in  the  bottom  of  the  hole. 
Deep  holes  should  be  cleaned  with  a  sand 
pump,  similar  to  that  shown  in  Fig  20, 
or  spoon  at  each  change  of  steel,  and  if 
the  hole  becomes  mudded  the  cleaning 
must  be  done  frequently. 


LUBRICATION.  —  When  starting  up  new 
air  drills  use  a  lubricant  consisting  of 
one  pint  of  cylinder  oil  to  one-fourth 
pound  of  flake  graphite,  applying  one 
tablespoonful  of  lubricant  for  each 
5-foot  hole  during  the  first  ten  shifts 
drilled.  After  this  use  a  good  grade  of 
drill  oil,  one  tablespoonful  for  each 
10-foot  hole  drilled.  Do  not  use  a  heavy 
grade  of  oil  with  air  drills,  as  such  oil 
freezes  readily  and  retards  the  machine. 

RUNNING  WITH  STEAM. 

SETTING  UP  AND  STARTING.  —  What- 
ever  the  mounting,  it  must  be  firmly  se- 

47 


Rock    Excavati n g    a .  n d    B 1  a s  t i  n g 


cured.  If  the  drill  is  mounted  on  a  tripod  or 
quarry  bar  set  the  mounting  in  the  desired  posi- 
tion and  then  "spot"  a  small  hole  in  the  rock  with 
a  hand  drill  for  each  leg,  and  place  the  weights 
on  the-  legs.  Where  the  rock  is  so  soft  that  the 
jar  of  the  machine  causes  the  legs  to  cut  into 
the  stone,  and  thereby  throws  the  drill  out  of 
line  with  the  hole,  it  is  necessary  to  put  a  wooden 
block  under  each  leg.  An  iron  plate,  with  a 
hole  in  it  for  the  leg,  should  be  screwed  on 
each  block.  Where  compressed  air  is  used  the 
drill  will  start  at  once,  but  with  steam  it  will 
take  a  few  minutes  for  the  machine  to  become 
equally  heated. 

Do  not  strike  the  steam  chest  or  any  other  part 
of  the  drill,  or  loosen  any  bolt  or  side  rod,  for 
when  the  steam  chest  or  cylinder  becomes  suffi- 
ciently heated  the  drill  will  start.  Start  the  drill 
slowly  and  on  a  short  stroke,  as  noted  above. 

LUBRICATION. — The  general  instructions  for 
putting  in  upper  (or  dry)  and  down  (or  wet) 
holes  with  air  drills  apply  also  to  those  run  by 
steam. 

When  starting  a  steam  machine  which  has  been 
shut  down  some  time  do  not  oil  until  the  water  is 
all  out  of  it,  then  oil  often  and  in  small  quantities 
through  the  oiler  which  is  furnished  with  each 
machine.  Also  oil  the  drill  through  the  hole  in 
the  top  head.  Use  a  good  grade  of  cylinder  oil 
when  running  with  steam. 

48 


Rock    Excavating    and    Blasting 


GENERAL  SUGGESTIONS. 

In  soft  ground  in  both  wet  and  dry  holes  the 
drill  may  cut  into  the  rock  faster  than  it  can 
throw  the  cuttings  out  of  the  hole,  causing  mud- 
ding  or  clogging.  In  these  cases  always  throttle 
the  air  to  reduce  the  hardness  of  the  blow  and  use 
the  longest  possible  stroke. 

When  the  drill  strikes  a  cavity  or  seam  in  the 
rock  crank  the  machine  down  to  a  short  stroke, 
until  the  bit  has  started  in  the  next  ledge.  Do 
not  keep  the  machine  running  if  the  piston  stops 
rotating,  or  if  the  drill  stops  cutting.  If  a  tripod 
leg  has  worked  low,  causing  the  steel  to  bind  in 
the  hole,  straighten  it  up.  If  a  column  arm  is  too 
high  let  it  down,  or  vice  versa. 

Keep  the  drill  steel  running  freely  in  the  hole 
by  making  such  changes  in  the  position  of  the  drill 
on  its  mounting  as  may  be  required,  making  these 
changes  as  soon  as  the  steel  begins  to  bind.  Do 
not  wait  until  the  hole  has  become  crooked.  Avoid 
running  with  crooked  steels  or  shanks.  Have  the 
steel  tight  in  the  chuck  or  it  will  rapidly  wear  the 
chuck  bushing,  which  causes  the  drill  to  run  out 
of  center,  and  results  in  excessive  friction  and 
wearing  of  the  bit  on  the  sides  of  the  hole. 

ADJUSTMENTS.  —  In  starting  a  new  drill  care 
should  be  taken  that  all  adjustments  on  the  drill 
are  tight  and  secure,  and  they  should  be  kept  so 
at  all  times.  The  exhaust  pipe  should  be  screwed 
in  with  a  wrench  and  made  tight.  Otherwise  it 

49 


Rock    Excavating    and    Blasting 


will  jar  loose,  wearing  or  stripping  the  threads  so 
that  when  next  screwed  tight  it  may  partially 
choke  the  exhaust  passage.  The  steam-chest 
plugs,  or  buffers,  should  be  screwed  in  as  far  as 
they  will  go  and  the  check  nuts  which  hold  them 
in  place  then  made  tight.  After  running  for  a 
few  hours,  slack  off  the  check  nuts  and  tighten 
the  plugs  again.  These  buffers  do  not  form  any 
means  of  adjustment,  but  merely  afford  access  to 
the  valve. 


50 


CHAPTER  VI. 


ROCK  DRILL  BITS  OR  STEELS. 


OCR  DRILL  STEELS.  —  Too  much  em- 
phasis cannot  be  placed  on  the  im- 
portance of  using  suitable  drill 
steels  with  rock  drills.  The  bits 
must  be  properly  formed,  sharpened 
and  tempered  for  the  work  in  hand,  and  must  be 
of  the  right  gauge,  or  the  drilling  machine  can- 
not operate  to  advantage. 

A  typical  rock  drill  steel  is  shown  in  perspective 
in  Fig  21.  Other  drill  steels  differ  from  this  only 
in  the  length  of  the  ribs  or  wings,  the  angle  of 
the  cutting  edge  and  the  angles  at  which  the 
wings  cross  each  other. 

Experience  in  the  manufacture  and  use  of 
drilling  machines  shows  that  it  will  prove 
economical  to  secure  the  best  blacksmith  obtain- 
able to  care  for  the  drill  steels.  If  bits  of  the 
right  temper,  shape  and  sharpness  are  always  on 
hand  the  drills  will  be  able  to  work  constantly 
to  the  best  advantage,  whereas  delays  to  the  drills 
mean  losses  in  efficiency  to  the  whole  plant. 

For  general  mining  and  quarrying  purposes 
the  ordinary  cross-bit  is  recommended.  The 
proportions  of  the  bit,  as  to  length  and  thickness 

51 


Rock    Excavating    and    Blasting 


of  the  wings  or  ribs,  are  indicated  in  the  accom- 
panying illustrations.  Figs.  22  and  23  are  bits 
for  hard,  non-gritty  rock,  and  are  alike 
except  for  the  different  angles  shown  on 
the  cutting  edges.  Fig.  22  shows  about 
the  highest  angle  to  which  the  cutting 
edge  can  be  made  without  danger  of  break- 
ing. The  angle  shown  on  the  cutting  edge 
in  Fig.  23  is  one  of  many  which  may  be 
used  under  different  con- 
ditions without  any  other 
change  in  the  bit.  In 
cutting  hard  and  medium 
hard  rock,  sharp  drills 
and  a  wide-open  throttle 
may  be  used  to  good  ad- 
vantage, and  the  hole  will 
not  ordinarily  clog  with 
mud,  as  the  amount  of 
rock  loosened  by  each 
blow  is  so  little  that  it  is  pefspect- 
at  once  mixed  into  slush  lot  Rock 
by  the  water  in  the  hole.Drin 
The  sharp  rebound  of  the  drill 
when  striking  hard  rock,  to- 
gether with  the  positive  recovery 
of  the  machine,  quickly  gets  rid 
of  this  slush.  If  the  same  bits 
steel  for  Hard  and  drill  are  run  on  an  open 
Rock.  throttle  in  soft  or  even  medium- 

soft  ground  the  hole  soon  becomes  clogged.     The 
reason  for  this  is  that  while  the  hole  remains  the 

52 


Rock    Excavating    and    Blasting 


same  diameter  and  the  amount  of  water  for  mud- 
ding  purposes  is,  therefore,  the  same,  the  steel 
chips  out  three  or  four  times  as  much  dust  at  each 
blow  as  it  does  in  hard  rock.  The  rate  of  cutting 

: |    should,  therefore,  be  reduced 

in  order  to  keep  the  drill 
working  at  maximum  effi- 
ciency. The  speed  may  be 
regulated  by  throttling  the  air 
or  steam,  but  this  reduces  the 
rapidity  of  action  of  the  drill, 


Fig.  23. 

Drill  Steel  for  Soft 
Rock. 

so  that  it  does  not  always  mix 
into  slush  the  dust  caused, 
even  at  the  slower  speed.  The 
recoil  of  the  steel  from  soft 
rock  is  also  considerably  less. 
In  soft  rock  duller  bits  should 
be  used,  like  that  shown  in 
Fig.  23.  The  angle  of  the  cut- 
ting edge  may  be  even  duller 
than  this,  sometimes  almost 
square  on  the  end,  in  order  to 

53 


Fig.  24. 

Length  of  Rib  on  Drill 
lor   Soft    Rock. 


Rock    Excavating    and    Blasting 


secure  good  results.  In  connection  with  the  above 
subject  it  is  well  to  bear  in  mind  the  length  of 
the  wings  or  ribs  for  different  kinds  of  work. 
Figs.  22  and  23  show  extreme  lengths  for  very 
hard  rock,  intended  to  give  strength  and  hold  the 
gauge  as  long  as  it  is  necessary.  Figs.  24  and  25 

show  shorter  ribs,  which 
give  the  bit  more  clear- 
ance and  make  it  more 
tL___J  desirable      for      general 

"T  \~IM~~7  purposes.  Under  ordin- 
ary conditions  its  ability 
to  mix  mud  is  much 
greater  than  that  of  the 
long  bit  like  Fig.  22.  For 
drilling  dry  holes  in  tun- 
nel headings  or  else- 
where, the  bit  with  short 
ribs  has  less  tendency  to 
allow  the  hole  to  draw 
up.  The  wings  are  five- 
eighths  of  an  inch  thick, 
for  the  size  shown  in 
Figs.  22  to  25,  and  should  never  be  less  than  that 
for  this  size  of  bit  and  steel.  They  should  be 
the  same  thickness  throughout  to  allow  free 
return  of  the  cuttings.  If  gauge  less  than  2*4 
inches  is  desired  make  the  bit  correspondingly 
shorter. 

In  seamy  ground  the  bit  shown  in  Fig.  26 
will  occasionally  work  satisfactorily  when  a 
cross  bit  would  not  prevent  a  "rifled"  hole,  since 

54 


Fig.  25. 

Cutting  Edge  on  Drill  Steel 
for  Soft  Rock. 


Rock    Excavating    and    Blasting 


bit  strikes  only  half  as  often  as  the  "+" 
bit  in  a  given  spot.  Flat  or  chisel  bits  are  not 
recommended,  since  their  reaming  qualities  are 
poor,  and  while  cutting  faster  than  the  +  bit 
under  some  conditions  they  are  very  hard  on  the 
machine.  It  is  important  to  keep 
the  wings  square  at  the  corners,  as 
this  permits  the  gauge  of  the  hole 
to  be  properly  maintained.  Do  not 
use  a  set  of  steels  after  the  gauge 
has  begun  to  wear.  The  time  and 
trouble  taken  in  securing  fresh 
steel  amount  to  little  in  comparison 
with  the  delay  caused  by  trying  to 
work  down  a  hole  with  steel  that 
is  constantly  sticking,  to  say  noth- 
ing of  the  wear  and  tear  on  the 
machine.  Blacksmiths  should  take 
pains  to  furnish  bits  made  exactly 
to  the  required  gauge.  A  little 
neglect  in  this  particular  causes 
much  trouble  and  loss  of  time  with 
the  drill. 

On  any  rock  on  which  the  cut- 
ting edges  are  not  dulled  upon  the 
first  hole  a  system  should  be  de- 
vised by  the  foreman  or  superintendent  to  de- 
termine how  much  each  bit  will  do  without  too 
much  "hammer  help."  The  improvement  will  be 
very  pronounced. 

SIZE  AND  WEIGHTS  OF  DRILL  STEELS. — In  Table 
III  will  be  found  the  number  of  drill  steels  used 

55 


Fig.    26. 
X  Bit  Drill  Steel 


Rock    Excavatila,nd    Blasting 


TABLE  III. 

Weights  and  Specifications  of  Drill  Steels. 


For  Drill  "UA"-2  inches-  Feed  12  Inches 

(Size  of  Shank,  %  in.  3%  in.) 

Name  of  Each 
Part 

Regular 
Size  of  Gauge 
Inches 

Length  Steel 
Will  Cut 

Sizes  of 
Steel 
Inches 

Weight  in 
Pounds 

Starter 

IK 

1  ft.  0  in. 

% 

3K 

2d  length    . 

1% 

2  ft.  0  in. 

% 

5 

3d  length 

IK 

3  ft.  0  in. 

% 

6 

4th  length  .    . 

i^ 

4  ft.  0  in. 

% 

iy> 

5th  length      . 

5  ft.  0  in. 

A 

9 

For  Drill  "US"-2^  Inches-Feed  15  Inches 

(Size  of  Shank,  %  in.  x  4  in.) 

Name  of  Each 
Part 

Regular 
Size  of  Gauge 
Inches 

Length  Steel 
Will  Cut 

Size  of 
Steel 
Inches 

Weight  in 
Pounds 

Starter    .    .    . 

1% 

1  ft.  3  in. 

1 

5 

2d  length    .    . 

1% 

2  ft.  6  in. 

1 

9 

3d  length    .    . 

iy> 

3  ft.  9  in. 

% 

10 

4th  length  . 

1% 

5  ft.  0  in. 

% 

13 

5th  length 

IK 

6  ft.  3  in. 

% 

16 

For  Drill  "UR"-2K  Inches-Feed  20  Inches 

(Size  of  Shank,  %  in.  x  4K  in.) 

Name  of  Each 
Part 

Regular 
Size  of  Gauge 
Inches 

Length  Steel 
Will  Cut 

Size  of 
Steel 
Inches 

Weight  in 
Pounds 

Starter 

1% 

1  ft.  8  in. 

1 

7 

2d  length    . 

1% 

3  ft.  4  in. 

1 

11 

3d  length    . 

IK 

5  ft.  0  in. 

% 

13 

4th  length  . 

1% 

6  ft.  8  in. 

% 

17 

5th  length  . 

IK 

8  ft.  4  in. 

7/ 

21 

56 


Rock    Excavating    and    Blasting 


TABLE  III. — Continued. 
Weights  and  Specifications  of  Drill  Steels. 


For  Drills  "UC"  and  "UC11-2M  Inches-Feed  24  Inches 

(Size  of  Shank,  1  in.  x  4%  in.) 

Name  of  Each 
Part 

Regular 
Size  of  Gauge 
Inches 

Length  Steel 
Will  Cut 

Sizes  of 
Steel 
Inches 

Weight  in 
Pounds 

Starter    .   .   . 

2K 

2  ft.  0  in. 

IK 

10 

2d  length    .   . 

2 

4  ft.  0  in. 

1% 

18 

3d  length    .   . 

IK 

6  ft.  0  in. 

1 

20 

4th  length  .   . 

1% 

8  ft.  0  in. 

1 

30 

5th  length  .   . 

1% 

10  ft.  0  in. 

1 

35 

6th  length  .   . 

IM 

12  ft.  0  in. 

1 

35 

For  Drill  "UD"-3  Inches-Feed  24  Inches 

For  Drills  "UE2"  and  "UE11"-3K  Inches-Feed  24  Inches 

For  Drills  "UF2"  and  "UF11"—  3M  Inches—  Feed  24  Inches 

(Size  of  Shank,  1%  in.  x  4%  in. 

Name  of  Each 
Part 

Regular 
Size  of  Gauge 
Inches 

Length  Steel 
Will  Cut 

Sizes  of 
Steel 
Inches 

Weight  in 
Pounds 

Starter 

2K 

2  ft.  0  in. 

\y* 

11 

2d  length  .    . 

2% 

4  ft.  0  in. 

IK 

19 

3d  length  .   . 

2M 

6  ft.  0  in. 

IK 

23 

4th  length    . 

2K 

8  ft.  0  in. 

IK 

31 

5th  length    . 

2 

10  ft.  0  in. 

IK 

39 

6th  length    . 

IK 

12  ft.  0  in. 

IK 

47 

7th  length    . 

m 

14  ft.  0  in. 

IK 

55 

8th  length    . 

IK 

16  ft.  0  in. 

IK 

63 

9th  length    . 

IK 

18  ft.  0  in. 

IK 

71 

10th  length    . 

1% 

20  ft.  0  in. 

IK 

79 

57 


Rock    Excavating    and    Blasting 


TABLE  III. — Continued. 
Weights  and  Specifications  of  Drill  Steels. 


For  Drills  "UH"  and  "UH11"—  3%  Inches—  Feed  30  Inches 

(Size  of  Shank,  1%  in.  x  5^  in.) 

Name  of  Each 
Part 

Regular 
Size  of  Gauge 
Inches 

Length  Steel 
Will  Cut 

Size  of 
Steel 
Inches 

Weight  in 
Pounds 

Starter 

3 

2  ft.  6  in. 

1% 

18 

2d  length  . 

2% 

5  ft.  0  in. 

1% 

32 

3d  length  . 

2M 

7  ft.  0  in. 

IM 

37 

4th  length    . 

2% 

10  ft.  0  in. 

IM 

48 

5th  length 

2M 

12  ft.  6  in. 

IM 

59 

6th  length    . 

2% 

15  ft.  0  in. 

IM 

70 

7th  length    . 

2M 

17  ft.  6  in. 

IM 

81 

8th  length    . 

2% 

20  ft.  0  in. 

IM 

92 

9th  length    . 

2 

22  ft.  6  in. 

IM 

103 

10th  length 

1% 

25  ft.  0  in. 

IM 

114 

llth  length 

1% 

27  ft.  6  in. 

IM 

125 

For  Drill  "UH"—  3%  Inches-  Feed  24  Inches 

(Size  of  Shank,  I1/  in  x  5%  in.) 

Name  of  Each 
Part 

Regular 
Size  of  Gauge 
Inches 

Length  Steel 
Will  Cut 

Size  of 
Steel 
Inches 

Weight  in 
Pounds 

Starter 

3 

2  ft.  0  in. 

1% 

15 

2d  length  .    . 

2% 

4  ft.  0  in. 

1% 

25 

3d  length 

m 

6  ft.  0  in. 

IM 

31 

4th  length 

^% 

8  ft.  0  in. 

IM 

41 

5th  length 

2K 

10  ft.  0  in. 

IM 

50 

6th  length 

2% 

12  ft.  0  in. 

IM 

57 

7th  length    . 

2M 

14  ft.  0  in. 

IM 

63 

8th  length 

2^ 

16  ft.  0  in. 

IM 

76 

9th  length    . 

2 

18  ft.  0  in. 

IM 

82 

10th  length 

1% 

20  ft.  0  in. 

IM 

92 

58 


Rock    Excavating    and    Blasting 


TABLE  III.— Continued. 
Weights  and  Specifications  of  Drill  Steels. 


For  Drill  "UK"-  4^  Inches—  Feed  30  Inches 

(Size  of  Shank,  1%  in.  x  6  in.) 

Name  of  Each 
Part 

Regular 
Size  of  Gauge 
Inches 

Length  Steel 
Will  Cut 

Size  of 
Steel 
Inches 

Weight  in 
Pounds 

Starter 

3% 

2  ft.  6  in. 

1% 

27 

2d  length  . 

3K 

5  ft.  0  in. 

1% 

47 

3d  length  . 

3% 

7  ft.  6  in. 

IK 

66 

4th  length 

3^ 

10  ft.  0  in. 

IK 

74 

5th  length 

3K 

12  ft.  6  in. 

IK 

90 

6th  length 

3 

15  ft.  0  in. 

IK 

107 

7th  length 

2% 

17  ft.  6  in. 

IK 

123 

8th  length 

2% 

20  ft.  0  in. 

IK 

140 

9th  length 

2% 

22  ft.  6  in. 

IK 

156 

10th  length 

2K 

25  ft.  0  in. 

IK 

174 

llth  length 

2% 

27  ft.  6  in. 

IK 

190 

12th  length 

2M 

30  ft.  0  in. 

IK 

206 

13th  length 

2K 

32  ft.  6  in. 

IK 

222 

14th  length    . 

2 

35  ft.  0  in. 

IK 

238 

For  Drill  "UL"—  5  Inches-  Feed  30  Inches 

(Size  of  Shank,  1%  in.  x  6&  in.) 

Name  of  Each 
Part 

Regular 
Size  of  Gauge 
Inches 

Length  Steel 
Will  Cut 

Size  of 
Steel 
Inches 

Weight  in 
Pounds 

Starter    .   .   . 

4 

2  ft.  0  in. 

1% 

22 

2d  length      . 

3% 

4  ft.  6  in. 

1% 

39 

3d  length  .    . 

3% 

7  ft.  0  in. 

IK 

42 

4th  length    . 

3% 

9  ft.  6  in. 

IK 

65 

5th  length    . 

3K 

12  ft.  0  in. 

IK 

81 

6th  length    . 

3% 

14  ft.  6  in. 

IK 

98 

7th  length    . 

3K 

17  ft.  0  in. 

IK 

114 

8th  length    . 

3K 

19  ft.  6  in. 

IK 

131 

9th  length    . 

3 

22  ft.  0  in. 

IK 

148 

10th  length    . 

2% 

24  ft.  6  in. 

IK 

165 

llth  length    . 

2% 

27  ft.  0  in. 

IK 

182 

12th  length    . 

2% 

29  ft.  6  in. 

IK 

200 

13th  length 

2K 

32  ft.  0  in. 

IK 

217 

14th  length 

2% 

34  ft.  6  in. 

IK 

234 

15th  length    . 

2M 

37  ft.  0  in. 

IK 

251 

16th  length    . 

2 

39  ft.  6  in. 

IK 

268 

59 


Rock    Excavating    and    Blasting 


with  Sullivan  machines  of  various  sizes,  the 
lengths,  weights,  etc.  The  letters  at  the  top  of 
each  table  refer  to  the  size  of  the  rock  drill,  so 
that  full  information  can  be  had  by  referring 
back  to  Table  II.  For  instance,  the  "UA"  size, 
by  referring  to  Table  II,  will  be  found  to  have  a 
cylinder  2  inches  in  diameter  with  4i/2-inch 
stroke  and  length  of  feed  of  12  inches,  together 
with  all  necessary  data  as  to  sizes  of  steam  or  air 
inlets  and  outlets,  and  all  other  information  about 
the  machine. 

In  column  two  the  regular  size  of  gauge  in 
inches  refers  to  the  size  of  the  cutting  head  in 
end  of  the  bit. 

It  will  be  noticed  that  the  size  of  the  gauge,  or, 
in  other  words,  the  size  of  the  drill  head,  decreases 
in  size  with  each  length  added.  For  instance,  in 
the  last  size  of  drill  listed  in  this  table,  the  ma- 
chine starts  off  with  a  drill  that  will  make  a  hole 
four  inches  in  diameter,  and  each  time  the  drill  is 
changed  and  lengthened  the  size  of  the  bit  is  de- 
creased one-eighth  inch  in  diameter,  so  that  at  a 
depth  of  39  feet  6  inches  it  is  drilling  a  hole  only 
2  inches  in  diameter.  The  object  of  thus  decreas- 
ing the  size  of  drill  at  each  change  of  the  drill 
steels  is  to  prevent  the  drill  from  binding,  as 
would  be  the  case  if  the  attempt  were  made  to  use 
a  steel  with  the  same  size  bit  throughout  the  en- 
tire depth  of  the  hole. 

It  might  be  well  to  state  here  that  for  ordinary 
building  construction  it  will  seldom  be  necessary 
to  use  a  machine  that  will  drill  deeper  than  8  feet 

60 


Rock    Excavating    and    Blasting 


4  inches.  For  large  engineering  works  the  large 
size  drills  may  be  used,  but  for  ordinary  opera- 
tions the  smaller  sizes  will  be  found  to  give  satis- 
factory results. 

Drills  30  feet  in  length  and  over  are  generally 
made  in  two  parts  for  convenience  in  shipping  and 
handling,  but  can  be  had  in  one  piece  when  so  de- 
sired. 

BLACKSMITHS'  TOOLS  FOR  FORGING 
DRILL  STEELS. 

The  special  tools  required  by  a  blacksmith  for 
keeping  the  drill  steels  in  condition  are  shown  in 
the  following  eight  illustrations:  Fig.  27  is  a 
swage  for  forming  the  wings  of  the  drill  steel, 
Fig.  28  is  a  "sow"  for  gauging  the  wings,  Fig. 
29  is  a  cross-shaped  "dolly"  for  shaping  the  cut- 
ting end  of  the  drill  steels,  Fig.  30  is  an  X-shaped 
dolly  for  the  same  purpose,  Fig.  31  is  a  flatter, 
Fig.  32  is  a  spreader,  Fig.  33  is  a  drill  shank 
swage  for  anvil  and  Fig.  34  is  a  similar  swage  for 
a  hammer. 

AIR  REQUIRED  FOR  DRILLING  MACHINES. 

The  type  of  air  compressor  used  to  furnish  air 
for  the  machine  drills  will  depend  to  a  great  ex- 
tent upon  whether  the  work  is  of  a  permanent 
or  temporary  nature.  For  rock  drilling  in  quar- 
ries naturally  a  power  plant  will  be  required,  and 
a  stationary  air  compressor,  permanently  mounted 

61 


Rock    Excavating    and    Blasting 


62. 


Rock    Excavating    and    Blasting 


on  a  solid  base,  would  be  preferable.  For  tem- 
porary work  in  building  construction,  unless  the 
operation  is  a  particularly  large  one,  a  portable 
boiler  when  steam  is  to  be  used,  or  a  boiler,  engine 
and  air  compressor  when  air  is  to  be  used,  will 
be  found  the  more  convenient. 

The  size  of  the  compressor  required  will  depend 
upon  the  number  of  drills  that  are  to  be  operated, 
which  in  turn  determine  the  amount  of  free  air, 
that  is,  atmospheric  air,  which  must  be  compress- 
ed to  the  required  pressure.  Seventy-five  pounds 
is  a  common  pressure  to  supply  air  to  the  drills, 
and  in  Table  IV  can  be  found  the  number  of  cubic 
feet  of  free  air  required  to  run  from  one  to  forty 
drills. 

Allowance  has  been  made  in  the  table  for  the 
difference  between  piston  displacement  and  actual 
delivery,  so  that  no  further  deduction  need  be 
made  from  the  compressor  capacities  stated  in 
catalogue.  The  figures  represent  the  require- 
ments of  drills  under  ordinary  working  condi- 
tions. When  a  practice  is  made  of  drilling  deep 
holes,  or  where  special  conditions  render  the  work 
unusually  severe,  more  air  will  be  necessary.  It 
is,  therefore,  wise  in  purchasing  an  air  compres- 
sor to  allow  for  such  contingencies,  and  many  con- 
tractors, quarrymen  and  mine  managers  of  expe- 
rience invariably  install  a  compressor  capable  of 
furnishing  20  or  25  per  cent,  more  air  than  their 
machines  require. 

63 


Rock    Excavating    and    Blasting 


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Rock    Excavating    and    Blasting 


The  figures  given  in  Table  IV  are  for  air  at  75 
pounds  pressure  at  sea  level.  The  modern  ten- 
dency in  rock  drill  practice  is  toward  higher  pres- 
sures, and  the  present  standard  is  near  90  pounds. 
For  estimating  the  air  consumption  of  drills  at  any 
required  pressure  or  altitude  the  factors  of  mul- 
tiplication given  in  Table  V  will  be  found  conven- 
ient. 

These  tables  are  used  in  the  following  manner. 
Suppose,  for  instance,  instead  of  75  pounds  pres- 
sure, the  drill  is  to  operate  under  a  pressure  of 
only  60  pounds,  and  at  sea  level.  In  column  2, 
Table  IV,  it  will  be  seen  that  a  single  drill  requires 
55  cubic  feet  of  free  air  to  operate  at  75  pounds  of 
pressure.  According  to  the  factors  for  various 
altitudes  and  pressures  given  in  Table  V,  how- 
ever, it  would  require  only  .83  per  cent,  of  55,  or, 
.83  X  55  =  45.65  cubic  feet  of  air  per  minute. 

Suppose,  however,  that  instead  of  being  at  sea 
level  the  rock  drill  was  to  be  used  in  excavating 
on  the  top  or  side  of  a  mountain  at  an  elevation  of 
6,000  feet  above  the  level  of  the  sea.  In  that  case, 
instead  of  a  factor  of  .83  it  will  require  1.03  times 
as  much  air  to  operate  the  drill  under  a  pressure 
of  60  pounds  as  it  would  to  operate  the  same  drill 
at  sea  level  under  a  pressure  of  75  pounds.  At 
sea  level  and  at  75  pounds  pressure  the  drill  re- 
quires 55  cubic  feet  of  free  air,  therefore  at  an 
altitude  of  6,000  feet  and  under  60  pounds  pres- 
sure it  would  require  55  X  1.03  =  56.65  cubic  feet 
of  free  air  per  minute. 

65 


Rock    Excavating    and    Blasting 


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66 


Rock    Excavating    and    Blasting 


Take  another  example.  Instead  of  running  the 
rock  drill  with  air  at  75  pounds  pressure,  suppose 
100  pounds  pressure  be  used.  In  that  case  1.28 
times  as  much  free  air  would  be  required  as  when 
the  machine  is  operated  under  the  lower  pressure 
of  75  pounds  per  square  inch — 1.28  X  75  =  96 
cubic  feet  of  free  air  per  minute.  When  the  power 
plant  and  compressor  are  located  at  considerable 
distance  from  the  workings,  an  additional  allow- 
ance of  say  15  per  cent,  should  be  made  for  the 
loss  of  head  due  to  friction  of  the  pipes,  and  the 
loss  of  volume  due  to  condensation  or  contraction. 
Compressing  air  heats  it  so  that  it  expands  and 
occupies  more  space  than  it  would  if  compressed 
without  heat;  and  this  air  when  in  the  storage 
tank  and  being  conducted  through  pipes  to  the 
several  machines,  in  cold  climates  or  during  cold 
weather,  has  its  temperature  reduced  and  shrinks 
or  contracts  correspondingly  in  volume,  condens- 
ing, perhaps,  to  a  less  volume,  relatively,  than 
when  in  the  free  state. 

It  is  false  economy  to  try  to  operate  with  an 
inadequate  supply  of  air,  so  to  remedy  this  state 
of  affairs  it  is  well  to  have  a  compressor  with  a 
capacity  of  from  25%  to  40%  greater  than  that 
actually  required.  This  makes  the  plant  more 
elastic  likewise,  enabling  more  machines  to  be  run 
at  one  time  than  was  originally  planned,  a  condi- 
tion which  is  sometimes  necessary. 

On  large  machines,  like  stone  channelers,  it  has 
been  found  economical  to  use  re-heaters  for  heat- 
ing the  air  before  it  is  used  in  the  machine.  The 

67 


Rock    Excavating    and    Blasting 


re-heaters  not  only  increase  the  volume  of  air, 
thereby  increasing  the  supply  to  the  machine,  but 
it  also  keeps  the  moisture  in  the  air  from  freezing 
in  the  exhaust  ports,  an  occurrence  which  is  liable 
if  the  air  is  not  heated,  for  the  air  on  expansion, 
when  released  from  the  cylinders  of  the  channeler 
has  a  refrigerating  effect,  just  the  opposite  of  the 
heating  effect  due  to  compression.  It  is  the  cool- 
ing effect  of  expansion  which  causes  the  exhaust 
ports  of  machines  operated  by  compressed  air  to 
freeze,  and,  of  course,  the  higher  the  pressure  of 
the  air,  the  greater  the  cooling  effect  of  expansion. 


68 


CHAPTER  VII 


HAMMER  DRILLS. 

*          * 

N  blasting  work,  a  charge  of  explosive 
generally  throws  out  or  breaks  down 
blocks  of  rock  too  large  and  heavy 
for  removal.  When  such  is  the  case, 
"pop"  holes  must  be  drilled  in  them, 
and  the  rocks  broken  up  into  convenient  sizes  for 
handling  by  blasting  them  with  small  charges  of 
explosives.  Hand  drilling  was  formerly  employed 
for  this  purpose,  but  machine  hammer  drills,  op- 
erated by  one  man,  and  using  compressed  air,  are 
now  generally  used. 

Hammer  drills  are  handy  not  alone  for  breaking 
up  boulders  and  large  rock  fragments,  but  will  be 
found  convenient  for  cutting  hitches  in  rock  walls 
to  receive  timbers,  and  for  trimming  the  walls, 
roof  or  floor  of  tunnels,  shafts  or  cellar  excava- 
tions. They  can  likewise  be  used  to  good  advan- 
tage in  excavating  rock  in  narrow  sewer  or  water 
trenches,  where  light  weight,  compactness  and 
rapidity  of  setting  .up  go  a  long  way  toward  re- 
ducing the  cost  of  the  work. 

69 


Rock    Excavating    and    Blasting 


Hammer  drills  are  made  in  two  sizes.  The 
small  size  weighs  25  pounds  and  is  for  drilling 
holes  up  to  3  feet  in  depth,  and  large  enough  for 
ys-inch  powder.  The  large  drill  weighs  35  pounds 
and  will  drill  holes  3  feet  deep  and  large  enough 
for  1%-inch  powder. 

The  characteristic  feature  of  the  hammer  drill 
is  that  the  cutting  edge  of  the  steel  rests  against 
the  rock  all  the  time,  and  is  forced  into  it  by  the 
repeated  blows  of  the  piston,  which  is  independent 
or  detached  from  the  drill  steel,  and  is  driven  rap- 
idly back  and  forth  in  the  cylinder. 

The  weights,  dimensions  and  capacity  of  Sulli- 
van hammer  drills  can  be  found  in  Table  VI. 


TABLE  VI. 

Capacities  of  Hammer  Drills. 


Class  of  Drill 

DB-15 

DB-19 

Depths  to  which  holes  may  be  drilled 
(inches)                              ... 
Maximum  diameter  of  holes  (inches)    . 
Weight  of  drill  in  pounds              .... 
Size  of  hose  required  (inches) 
Size  of  shanks,   inches   (shank  is  hex- 
agonal) 

36 

IK 
25 
7-16 

%x3 

60 

2 
35 

1A 

lx3K 

For  the  classes  of  work  for  which  they  are  used 
the  hammer  drill  has  important  advantages  in  its 
light  weight,  the  ease  and  rapidity  with  which 
it  can  be  set  up  and  handled,  its  high  drilling 
speed  and  economy  of  power. 

These  machines  or  tools  are  so  light  they  can  be 
handled  readily  by  one  man,  and  as  no  tripod, 
column  or  other  mounting  is  required  no  time  is 

70 


Rock    Excavating    and    Blasting 


lost  in  setting  up  or  in  removing  the  drills  from 
one  point  to  another. 

They  are  so  light  and  compact  that  they  can  be 
carried  wherever  a  man  can  go,  and  in  narrow 
trench  work  the  openings  need  be  driven  only 
wide  enough  to  permit  a  man  to  enter.  Holes 
may  be  drilled  at  any  point,  at  any  angle,  or  in 
any  direction. 

Some  idea  of  the  capacity  of  these  hammer 
drills  may  be  obtained  from  past  performances. 
In  oolitic  limestone  of  varying  hardness,  very  ir- 
regular, full  of  mud  pockets  and  often  covered 
with  water,  twelve  of  the  smaller  hammer  drills 
each  averaged  forty  holes  18  inches  deep  per  shift 
of  10  hours.  The  best  record  was  100  holes  18 
inches  deep  or  150  feet  of  drilling,  while  36  holes 
3%  feet  deep  were  drilled  by  one  tool  in  seven 
hours.  Hammer  drills  are  now  being  used  to  a 
considerable  extent  in  mine  work  for  drifting, 
owing  to  the  time  saved  after  a  shot.  The  driller 
can  put  in  his  upper  holes  from  the  top  of  the 
muck  pile  while  the  mucker  is  at  work  loading  out 
the  heaps.  The  lifters  are  then  put  in  last  after 
the  muck  has  all  been  removed.  The  great  ad- 
vantage in  using  hammer  drills  for  work  of  this 
class  lies  in  the  fact  that  no  time  is  lost  in  muck- 
ing for  the  "set-up"  as  in  the  case  of  piston  drills, 
or  in  mounting  the  drills  afterwards  on  the  bars 
or  columns. 


71 


Rock    Excavating    and    Blasting 


"Plug"  and  "foot  hole"  drills  of  the  hammer 
type  are  made  in  two  sizes  for  drilling  "plug"  and 
"foot  holes." 

The  smaller  hammer  is  for  drilling  holes  up  to 
6  inches  in  depth,  and  the  larger  one  for  holes 
up  to  12  inches  in  depth.  A  hammer  drill  of  this 
type,  which  differs  but  slightly  from  those  just 
described,  is  shown  in  Fig. 
35.  This  tool  employs  solid 
steels  or  bits,  while  the 
larger  size  uses  hollow  drill 
steels.  The  solid  steel, 
shown  in  the  illustration, 
is  rotated  by  a  hand  wrench 
shown  sticking  out  to  the 
left  of  the  drill  steel,  and 
the  hole  is  kept  free  from 
dust  by  exhaust  air 
from  the  drill,  which 
is  directed  into  it  by  the 
blower  hose  shown,  con- 
necting the  exhaust  port  to 
the  flange,  near  the  end  of 
the  drill  steel.  When  start- 
ing a  hole  the  valve  is  open- 
ed, exhausting  into  the  at- 
mosphere, to  avoid  the  an- 
noyance of  flying  stone  Fig.  35. 
dust.  After  the  hole  is 

started  a  small  amount  of  exhaust  air  is  allowed 
to  flow  into  the  hole.  As  the  hole  is  deepened 
more  and  more  exhaust  air  is  deflected  into  the 

72 


Rock    Excavating    and    Blasting 


opening,  all  being  used  in  this  way  if  desired. 
This  will  keep  the  bit  free  from  dust  and  dirt, 
even  in  broken,  wet  and  seaming  ground. 

A  solid  drill  steel,  such  as  is  used  in  a 
hammer  drill  for  drilling  "pop"  holes  for 
breaking  up  boulders  and  rock  fragments, 
is  shown  in  Fig.  36,  and  the  method  of 
using  the  hammer  drill  is  shown  in  Fig. 
37. 

Some  idea  of  the  capaci- 
ties   of    the    "plug"    and 

Steel  for' Hammer  "foot    hole"    drills    Can    be 

Dri11-  gained  from  the  following 

statement  of  what  they  have  accomplished. 
In  Barre  granite  the  "foot  hole"  drill  op- 
erating with  air  pressure  of  100  pounds 
drilled  a  1^-inch  hole  6  inches  deep  in  one 
minute,  while  the  "plug"  drill,  operating 
under  the  same  conditions,  has  put  in  160 
holes  %-inch  diameter  and  3  inches  deep 
in  one  hour.  Of  course,  the  work  one  of 
these  hammer  drills  will  accomplish  will 
depend  upon  the  character  and  quality  of 
the  rock,  the  skill  of  the  workman  hand- 
ling it,  and  the  air  pressure  supplied  at 
the  valve.  The  foregoing  statement  of  what  they 
have  already  accomplished,  however,  ought  to 
serve  as  a  guide  to  what  they  can  do,  keeping  in 
mind,  of  course,  the  fact  that  rock  varies  so  that 
it  is  seldom  the  same  in  any  two  cases,  and  the 
difference  in  quality,  fissures,  etc.,  must  be  taken 
into  consideration. 

73 


Excavating    and    Blasting 


Fig.  37. 
Method  of  Using  Hammer  Drill. 


74 


CHAPTER  VIII. 


STONE  CHANNELERS. 


0  work  on  rock  excavating  would  be 
complete  without  some  reference  to 
stone  channelers  for  engineering 
and  architectural  works.  For  over 
forty  years  machines  of  this  kind 
have  been  used  in  quarry  work,  and  for  many 
years  engineers  have  considered  channeling  ma- 
chines indispensable  when  rock  has  to  be  cut 
away  for  canals,  locks,  wheel  pits,  railroad  cuts 
or  similar  excavations.  More  recently  still  they 
have  been  used  in  architectural  works,  the  new 
Pennsylvania  Station  in  New  York  City  and  the 
sub-grade  terminal  yards  of  the  New  York  Cen- 
tral Railroad  at  Forty-second  street  being  notable 
examples. 

The  channeling  machine  has  advantages  of 
economy  and  utility  for  certain  classes  of  work 
which  put  them  in  a  class  by  themselves.  For 
instance,  the  smooth,  straight,  solid  walls  cut  by 
a  channeler  are  better  in  many  ways  than  the 
jagged  wall  left  after  drilling  and  blasting. 

The  channeler  cuts  exactly  to  the  surveyed  line 
of  the  work,  a  matter  which  is  difficult  to  accom- 

75 


Rock    Excavating    and    Blasting 


plish  when  the  wall  is  made  by  drilling  and  blast- 
ing. In  the  latter  case  too  much  rock  is  removed 
at  some  points  and  the  cavities  so  formed  must 
be  filled  with  concrete  or  masonry.  At  other  points 
projections  are  left  which  must  be  trimmed  off  to 
the  survey  line.  A  further  advantage  lies  in  the 
fact  that  the  cut  made  by  a  channeler  affords  an 
additional  free  face  for  the  powder  used  in  blast- 
ing to  act  against,  thereby  making  the  blasting 
easier  and  reducing  the  amount  of  explosive 
needed. 

The  wall  left  by  the  channeler  and  the  rock  back 
of  the  channeled  face  remain  as  solid  as  the  rock 
strata  themselves,  since  they  are  not  weakened 
or  shattered  by  explosives. 

Under  many  conditions  a  blasted  wall  needs  to 
be  sloped  away  from  the  line  of  excavation,  in 
order  to  prevent  slides,  thereby  making  necessary 
a  large  amount  of  extra  blasting.  Oftentimes 
rock-blasted  walls  must  have  retaining  walls  to 
prevent  rock  falls  or  slips,  and  they  are  greatly 
affected  by  weather,  water  freezing  in  the  crevices 
caused  by  the  shattering  effect  of  the  explosive 
and  heaving  the  loose  particles  out  of  place.  Chan- 
neled walls,  on  the  other  hand,  are  but  little  af- 
fected by  weather  and  will  stand  without  deterior- 
ation for  an  indefinite  length  of  time. 

Finally,  in  thickly  built-up  districts,  where  it 
is  necessary  to  excavate  rock  close  to  the  foun- 
dations of  existing  structures,  channeling  around 
the  sides  of  the  excavation  close  to  the  buildings 
is  desirable,  as  it  completely  isolates  the  rock  in- 

76 


Rock    Excavating    and    Blasting 


Fig.  38. 
Simplex  Channeling  Machine. 


77 


Rock    Excavating    and    Blasting 


side  of  the  cellar  space,  which  can  then  be  drilled 
and  blasted  without  damaging  the  foundations  of 
the  near-by  buildings. 

The  usefulness  of  channelers  is  limited  to  the 
softer  kinds  of  rock,  and  cannot  successfully  be 
used  for  channeling  trap  rock,  granite  or  hard 
gneiss.  They  can  be  successfully  and  economically 
employed,  though,  on  marble,  sandstone,  lime- 
stone, slate,  soapstone  and  for  the  softer  gneisses, 
such  as  that  underlying  New  York  City,  also  the 
softer  porphyries  and  granites. 

SIMPLEX  CHANNELING  MACHINES.  —  A  Sullivan 
direct-acting  simplex  channeling  machine,  mount- 
ed on  a  movable  truck,  together  with  a  boiler  for 
furnishing  steam,  is  shown  in  Fig.  38.  The  truck 
runs  on  steel  rails,  which  keep  the  machine  in 
alignment  for  the  channel  it  is  cutting,  and  at  the 
same  time  permits  it  to  be  easily  moved  from  one 
position  to  another.  The  channel-cutting  drill 
steels  are  shown  extending  below  the  level  of  the 
rails.  These  drill  steels  are  in  groups  of  five, 
working  so  close  together  that  the  holes  they  make 
run  together  into  one  continuous  slot. 

After  the  gang  drills  have  cut  a  groove  to  the 
required  depth  the  machine  is  moved  along  so 
that  the  next  set  of  holes  will  form  a  continuation 
of  the  slot  already  made.  The  cutting  or  chopping 
engine  which  operates  the  drill  steels  is  raised  or 
lowered  on  its  standard  by  means  of  a  feed  screw, 
in  a  manner  similar  to  that  employed  for  the  ordi- 
nary tripod-mounted  rock  drill.  Machines  of  this 

78 


Rock    Excavating    and    Blasting 


- 
si 


79 


Rock    Excavating    and    Blasting 


type  can  be  used  to  cut  not  only  vertically,  but 
likewise  at  any  angle  up  to  23  degrees. 

DUPLEX  CHANNELING  MACHINES. — A  duplex 
channeling  machine  of  the  same  make  as  the  sim- 
plex machine  is  shown  in  Fig.  39.  With  this  chan- 
neler  two  sets  of  gang  drills  are  used,  so  that 
double  the  amount  of  groove  is  being  cut  at  one 
time  that  is  possible  with  a  simplex  machine. 
Further,  this  channeler  is  designed  to  cut  grooves 
at  various  angles,  and  although  shown  in  the  il- 
lustration set  up  ready  to  channel  a  vertical 
groove,  by  adjusting  the  mounting  frame  on  the 
round  bar  seen  in  the  foreground  the  chisels  can 
be  tilted  to  any  desired  angle  up  to  39  degrees,  and 
by  means  of  special  braces  can  be  adjusted  to  cut 
angles  as  high  as  90  degrees  from  the  vertical. 
In  other  words,  the  machine  has  a  range  of  from 
vertical,  or  straight  down,  to  a  horizontal  position. 

Duplex  channeling  machines  can  be  had  with 
or  without  air  reheaters.  The  one  shown  in  the 
illustration  is  without  a  reheater,  although  there 
are  conditions  under  which  it  is  of  great  advan- 
tage to  have  the  air  reheated  before  delivering  it 
to  the  engine. 

DRILL  STEELS  FOR  CHANNELING  MACHINES. — 
The  drill  steels  used  for  channeling  are  consid- 
erably different  from  those  used  in  ordinary  rock 
drilling  machines,  and,  in  fact,  differ  from  one 
another  according  to  the  character  of  the  rock 
they  are  to  be  used  upon.  A  five-piece  gang  of 

80 


Rock    Excavating    and    Blasting 


81 


Rock    Excavating    and    Blasting 


steels  suitable  for  working  marble  is  shown  in 
Fig.  40.  The  illustration  shows  clearly  the  way 
the  drills  are  sharpened  and  set  in  relation  to  one 
another. 

A  three-piece  gang  of  drill  steels  for  a  chan- 
neling machine  working  in  crystallized  and  other 
limestone  is  shown  in  Fig.  41. 

A  gang  drill  of  three  pieces  for  channeling  slate 
is  shown  in  Fig.  42,  which  also  illustrates  the 
way  the  steels  are  set  in  relation  to  one  another. 


Fig.  44. 
Channeled  Walls  of  Chicago  Drainage  Canal. 

In  Fig.  43  we  have  a  solid  Z-shaped  bit,  or  drill 
steel,  which  has  been  adopted  by  the  manufac- 
turers and  is  recommended  by  them  for  engineer- 
ing and  architectural  works,  particularly  where 
the  cuttings  are  deep  and  the  rock  is  broken  or 
fissured. 

82 


Rock    Excavating    and    Blasting 


83 


Rock    Excavating    and    Blasting 


ILLUSTRATIONS  OF  CHANNELED  WORK. — Some 
idea  of  the  appearance  of  channeled  walls  can  be 
obtained  from  the  accompanying  illustration,  Fig. 
44,  which  shows  a  curve  in  the  Chicago  drainage 
channel,  which  was  channeled  out  of  the  solid 
Joliet  limestone. 

No  other  illustration  perhaps  would  convey  such 
a  good  understanding  of  what  can  be  accomplish- 
ed by  a  channeling  machine  as  this  solid  bank  of 
rock  rising  perpendicularly  from  the  water  and 
presenting  smooth  walls,  free  from  pockets  or 
projections  to  impede  the  flow  of  water. 

Another  view  which  shows  how  dimension  rocks 
can  be  taken  out  of  a  quarry  for  building  purposes 
is  shown  in  Fig.  45.  Two  channeling  machines 
may  be  seen  in  the  background  making  the  ver- 
tical cuts,  while  the  free  face  of  the  bench  of  rock 
shows  the  smooth  surface  of  the  cut,  made  by  the 
channeling  bits. 

The  sizes,  weights  and  specifications  of  Sullivan 
stone  channels  can  be  found  in  Table  VII. 

AIR  REHEATERS. — When  channelers  are  to  be  op- 
erated by  air  power  the  use  of  a  reheater  is  strong- 
ly advised.  A  saving  of  from  15  to  25  per  cent, 
in  power  may  be  attained  by  reheating  the  com- 
pressed air  before  it  is  used  in  the  channeler  en- 
gine, and  freezing  at  the  exhaust  is  also  prevented 
by  this  means. 

SPECIFICATION  OF  STEEL  FOR  CHANNELING  MA- 
CHINES.— As  has  already  been  pointed  out,  the 
type  of  drill  steels  varies  with  the  work  it  is  to 

84 


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do  and  the  machine  with  which  it  will  be  used. 
In  Table  VIII  will  be  found  full  information  on 
the  subject,  pointing  out  the  kind  of  drill  steel, 
length,  dimensions,  number  used  in  a  gang  and 
other  information  for  different  kinds  of  work. 

CAPACITIES  OF  CHANNELING  MACHINES. — For 
large  engineering  and  architectural  works  chan- 
nelers  are  made  which  will  successfully  cut  to  a 
depth  of  16  feet.  For  ordinary  practice,  however, 
a  depth  of  from  9  to  12  feet  is  about  all  that  will 
be  required.  After  taking  out  rock  to  the  9,  12 
or  16-foot  level  the  channeler  can  be  lowered  to 
the  next  bench  and  another  depth  channeled. 

The  cutting  speed  of  channeling  machines  var- 
ies within  wide  limits,  depending  upon  the  hard- 
ness of  the  stone,  freedom  from  fissures  or  other 
irregularities,  and  to  a  considerable  extent  the 
skill  of  the  operator.  Instead  of  giving  averages 
of  various  machines  it  is  considered  better  to  give 
the  actual  performances  of  the  several  machines 
listed  in  Table  VII,  as  furnished  by  the  manufac- 
turer, so  that  the  actual  capacity  of  any  of  the 
machines  listed  can  be  judged.  The  class  letters, 
Z,  Y,  etc.,  refer  to  the  sizes  and  specifications  of 
channeling  machines. 

At  Brandon,  Vt.,  a  "61/2"  channeler  has  aver- 
aged 1,485  feet  per  month,  and  a  "Z"  1,677  feet 
for  twelve  consecutive  months.  This  is  the  hard- 
est marble  in  the  State.  At  West  Rutland  a  "6i/2" 
channeler  has  cut  2,652,  2,649,  2,287  and  2,449 
square  feet  in  four  consecutive  months,  or  about 
100  feet  per  ten-hour  day. 

86 


Rock    Excavating    and    Blasting 


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The  double-head  machine  will  cut  from  40  to  50 
per  cent,  more  than  this.  In  Georgia  marble  220 
square  feet  have  been  channeled  in  7y%  hours  with 
a  double-head  "6i/2"  channeler.  In  the  Tennessee 
district,  where  single-head  channels  are  the  stand- 
ard, 80  feet  per  day  is  considered  a  fair  average 
for  a  season's  channeling,  taking  into  account  de- 
lays and  other  loss  of  time.  A  good  day's  work 
will  often  run  as  high  as  115  or  even  140  feet  per 
day. 

In  the  Indiana  Bedford  oolitic  limestone  the 
"Class  Y"  channeler  will  cut  from  200  to  350 
square  feet  in  opening  up  a  quarry,  when  the 
stone  is  rough  and  uneven.  In  developed  quarries 
the  improved  machines  will  cut  from  400  to  700 
feet,  depending  on  the  length  of  runs  and  the  even- 
ness of  the  stone.  In  the  Carthage,  Mo.,  district, 
where  the  stone  is  much  harder,  125  to  150  feet 
is  the  limit  of  the  "Y"  machine's  capacity,  when 
operating  with  140  pounds  boiler  pressure.  In 
Joliet  limestone  a  record  of  forty  consecutive 
shifts,  made  with  one  "Y"  channeler,  on  the  tur- 
bine-wheel pits  for  the  drainage-canal  power 
house,  in  1905,  showed  an  average  per  ten-hour 
shift  of  210  feet,  with  a  high  run  of  382  feet  in 
twelve  hours. 

In  the  Batesville,  Ark.,  field,  where  the  crys- 
tallized limestone  is  hard  and  close  grained,  the 
"Z"  machine,  with  boiler  attached,  makes  an  av- 
erage of  130  feet  per  day,  and  has  cut  as  high  as 
250  feet  on  a  test  run.  The  "Z"  in  the  tough 
sandstone  found  at  the  "Soo,"  using  a  "Z"  bit, 


Rock    Excavating    and    Blasting 


and  putting  in  cuts  from  9  to  12  feet  deep,  aver- 
aged from  60  to  75  feet  under  usual  conditions, 
but  when  given  long  runs  was  able  to  make  150 
feet  in  a  day.  In  channeling  gneiss,  which  is  prac- 
tically a  soft  granite  formation,  in  New  York 
City,  the  "Y-S"  channeler,  with  air  reheater,  aver- 
aged from  60  to  75  feet  per  day  of  eight  hours. 

The  "VX"  machine,  in  channeling  Vermont  or 
Pennsylvania  slate,  operating  on  a  steam  pres- 
sure of  100  pounds,  will  cut,  month  in  and  month 
out,  60  to  75  feet  per  day,  and  under  favorable 
conditions  will  run  as  high  as  100  to  125  feet. 
The  soft  soapstone  in  which  the  "6i/2"  and  "VX" 
channelers  are  used  in  Virginia  is  cut  at  the  rate 
of  150  to  250  feet  with  the  "VX,"  and  from  175 
to  350  feet  with  the  "61/2"  machine,  depending 
upon  the  hardness  of  the  veins.  In  engineering 
and  architectural  works,  to  judge  the  comparative 
cost  of  channeling  along  the  outer  boundry  of 
an  excavation,  and  removing  the  rock  along  the 
same  line  of  survey  by  means  of  rock  drills  and 
blasting,  the  cost  of  a  retaining  wall,  when  neces- 
sary, must  be  added  to  the  cost  of  removing  the 
rock  by  blasting.  A  retaining  wall,  or  other 
means,  must  often  be  employed  to  face  the  rough 
surface  of  a  cut  made  by  explosives,  while  no 
such  work  is  necessary  along  a  channeled  wall. 

Where  a  wall  has  been  channeled,  the  undis- 
turbed rock  alongside  of  the  cut  is  as  strong  and 
firm  as  before  channeling.  When  explosives  are 
used,  on  the  other  hand,  for  a  distance  back  from 
the  face  of  the  wall  the  rock  is  more  or  less  shat- 

89 


Rock    Excavating    and    Blasting 


tered,  the  extent  of  the  shattering  depending  to  a 
great  extent  on  the  care  with  which  the  work 
was  done,  and  the  skill  of  the  rock-men. 

At  its  best  a  blasted  wall  presents  a  rough, 
jagged  surface,  which  for  some  purposes  is  ob- 
jectionable and  possesses  economic  disadvantages. 
For  instance,  flumes,  mill  races,  canals,  and  chan- 
nels of  all  kinds  will  conduct  a  greater  amount  of 
water,  size  for  size,  under  the  same  head,  when 
the  walls  are  channeled,  for  they  then  present 
less  frictional  resistance  to  the  flow  of  water 
through  them. 

Again,  with  a  channeling  machine  rock  can  be 
excavated  right  to  the  surveyed  line,  and  the  cut 
is  as  smooth  as  the  surface  of  a  masonry  wall. 
To  work  right  to  the  line  with  drilling  machine 
and  explosives  is  not  so  easy  a  task,  and  when 
completed,  if  well  done,  is  perhaps  no  cheaper 
than  the  channeled  wall. 


90 


PART  III. 


EXPLOSIVES  USED  IN  BLASTING 

•$9  <$? 

CHAPTER  IX. 
POWDER. 


HERE  are  many  different  kinds  of 
explosives  used  for  different  pur- 
poses, such  as  mining,  army  and 
navy,  hunting,  quarrying  and  in  en- 
gineering works.  For  mining  where 
there  is  danger  of  gas,  flameless  or  safety  explo- 
sives are  used.  For  army  and  navy  uses  smoke- 
less powders  are  used,  while  the  various  explo- 
sives so  employed  are  sub-divided  into  different 
grades  and  classes.  For  the  purpose  of  rock  ex- 
cavating, however,  the  consideration  of  explosives 
can  be  confined  to  blasting  powders  and  dyna- 
mites, those  being  the  two  kinds  of  explosives 
commonly  used. 

HIGH  EXPLOSIVES  AND  Low  EXPLOSIVES.  —  Ex- 
plosives are  classified  in  practice  as  high  explo- 
sives and  low  explosives,  and  this  classification 

91 


Rock    Excavating    and    Blast  ing 


separates  the  materials  into  blasting  powder  and 
dynamite. 

Blasting  powder  is  classed  as  a  "low  explosive" 
because  it  is  exploded  by  a  spark,  flame  or  other 
means  of  generating  a  sufficiently  high  tempera- 
ture, whereas  "high  explosives"  are  detonated  by 
the  powerful  shock  of  a  blasting  cap  or  electric 
fuse.  Low  explosives,  or  blasting  powders,  are 
slower  in  action  than  high  explosives  of  the  dyna- 
mite group,  and,  consequently,  are  less  likely  to 
shatter  the  material  blasted. 

COMPOSITION  OF  BLASTING  POWDERS.  —  All  pow- 
ders of  the  nitrate  group,  whether  gunpowder  or 
blasting  powder,   are  frequently  referred  to   as 
black  powder.  Gunpowder,  the  most  familiar  type 
of  powder,  consists  of  an  intimate  mechanical  mix- 
ture of  potassium  nitrate,  charcoal  and  sulphur 
in  the  following  proportions  by  weight  : 

Parts 
Potassium  nitrate  .......................     75 

Charcoal  ...............................      15 

Suphur   ................................      10 

Total  ..............................    100 

Ordinary  blasting  powder  contains  the  same 
constituents  as  gunpowder,  but  in  different  pro- 
portions. 

The  composition  of  blasting  powder  averages  as 
follows,  different  manufacturers  using  slightly  dif- 
ferent proportions: 

92 


Rock    Excavating    and    Blasting 


Parts  Parts  Parts 
Potassium  or  sodium  nitrate  .  .     65         76         66 

Sulphur    20         14         11 

Charcoal  .  15         10         23 


Totals   ;  100       100 


100 


There  are  two  grades  of  blasting  powders  made, 
which  are  classed  by  the  DuPont  Company  as 


Fig.  46. 
Group   of  '.'A"   Powders. 


"A"  and  "B."  The  "A"  powders  are  made  of 
saltpetre  and  the  "B"  powders  of  nitrate  of  soda. 
Both  are  made  in  several  standard  granulations, 
or  sizes  of  grains,  as  shown  in  Fig.  46,  which  il- 
lustrates the  several  granulations  of  "A"  powders, 
listed,  according  to  their  letters,  C,  F,  FF,  etc. 
The  lower  the  letter  in  the  alphabet  the  coarser 
the  grain  of  the  powder,  and  the  greater  the  num- 

93 


Rock    Excavating    and    Blasting 


ber  of  letters  used  to  designate  a  grade  the  finer 
is  the  powder. 

The  various  granulations  of  "B"  powder  can  be 
seen  in  Fig.  47. 


Fig.  47. 

Group  of  "B"  Powders. 
94 


Rock    Excavating    and    Blasting 


An  important  fact  about  powders  to  bear  in 
mind  is  that  the  finer  the  granulations  the  quicker 
the  powder  will  act,  consequently  the  more  shat- 
tering the  effect  on  the  material  blasted.  "A" 
powders  and  "B"  powders  are  both  made  either 
glazed  (polished)  or  unglazed.  Glazed  or  polished 
blasting  powder  withstands  dampness  or  moisture 
better  than  unglazed,  and  will  run  more  freely, 
therefore  more  of  it  can  be  put  in  a  bore  hole  or 
pocket  of  given  size.  On  the  other  hand,  glazed 
blasting  powder  gives  off  a  little  more  smoke  than 
unglazed  powder.  Blasting  powder  will  not  give 
the  best  results  unless  the  drill  hole  in  which  it  is 
charged  is  carefully  and  compactly  tamped  to  a 
depth  sufficient  to  prevent  a  blowout.  Further- 
more, it  is  quickly  affected  by  moisture,  both  in 
storage  and  in  use,  and  care  must  always  be  taken 
to  keep  it  dry.  It  cannot  be  used  to  advantage  in 
wet  works. 

"A,"  or  saltpetre,  blasting  powder  is  somewhat 
stronger  and  quicker  in  action  than  "B"  blasting 
powder.  It  also  withstands  moisture  better.  It 
is  used  principally  in  marble  or  other  dimension 
stone  quarries,  where  conditions  are  such  that 
"B,"  or  nitrate  of  soda,  blasting  powder  would  not 
be  sufficiently  strong  to  give  satisfactory  results, 
and  where  high  explosives  would  shatter  the  ma- 
terial too  much. 

"B,"  or  nitrate  of  soda,  blasting  powder  is  very 
slow  in  action  and  is  used  in  coal  mines  where  gas 
and  coal  dust  are  not  met  with  in  sufficient  quan- 
tities to  cause  dangerous  explosions.  It  is  so  slow 

95 


Rock    Excavating    and    Blasting*     &etf® 

in  its  action  that  it  lifts  and  pushes  the  coal  out 
in  large  lumps  and  breaks  it  up  but  little  if  prop- 
erly used.  Granulations  from  FF  to  CCC  are  gen- 
erally used  in  coal  blasting,  although  FFF  is  some- 
times necessary  for  hard  coal. 

The  finer  granulations  of  blasting  powder,  also 
a  mixed  granulation  known  as  "railroad  powder," 
is  commonly  used  for  engineering,  architectural 
and  other  open-cut  work,  where  the  material  is  not 
particularly  hard.  "Railroad"  blasting  powder  is 
a  mixture  of  all  the  granulations  of  B  powder 
from  F  or  FF  to  FFF  inclusive,  for  which  reason 
it  is  possible  to  get  a  greater  weight  of  it  in  a 
given  space,  as  the  smaller  grades  fill  the  spaces 
between  the  larger  grains.  This  makes  a  mixed 
powder  especially  valuable  in  large  blasts,  where 
it  is  desired  to  shake  down  a  large  amount  of 
material  for  removal  by  means  of  steam  shovels. 

PROPERTIES  OF  BLASTING  POWDERS. — As  black 
powder  is  a  deflagrating,  not  a  detonating,  explo- 
sive, its  quickness  depends  upon  its  rate  of  burn- 
ing. By  a  deflagrating  explosive  is  meant  an  ex- 
plosive that  does  its  work  by  an  extremely  quick 
burning  of  its  ingredients  to  form  gases,  in  differ- 
entiation from  those  explosives  known  as  "high 
explosives,"  which  are  instantaneously  converted 
into  gases  by  means  of  a  blasting  cap  or  electric 
fuse.  The  "B"  blasting  powders  are  slower  in 
their  action  than  the  corresponding  sizes  of  "A" 
blasting  powders,  consequently  do  not  seem  to  be 
so  "strong."  The  "B"  blasting  powders  are  recom- 

96 


Rock    Excavating    and    Blasting 


mended  wherever  a  particularly  slow  powder  is 
required,  such  as  blasting  coal,  particularly  bit- 
uminous coal,  earth,  soft  or  rotten  rock,  etc. 

Although  both  grades  of  black  powder  are 
ruined  by  contact  with  water  the  "A"  blasting 
powders  are  less  susceptible  to  the  moisture  of 
the  atmosphere  than  the  "B"  blasting  powders. 
If  necessarily  exposed  to  damp  air,  or  stored  in  a 
damp  place,  the  "A"  blasting  powders  will  retain 
their  qualities  for  a  considerably  longer  time,  and 
should,  therefore,  be  used  in  tropical  climates 
where  the  air  is  heavily  charged  with  moisture, 
or  wherever  the  powder  in  storage  or  in  use  is  to 
be  exposed  to  unusual  climatic  conditions. 

As  has  already  been  mentioned,  black  powder 
is  a  deflagrating  explosive,  and  its  quickness  can 
be  varied  by  changing  its  rate  of  burning.  A 
certain  number  of  large  grains  present  less  sur- 
face for  ignition  than  an  equal  weight  of  smaller 
grains;  thus  the  smaller-grained  black  powders 
burn  faster  and  are  quicker  in  their  action  than 
larger-grained  powder  of  the  same  quality. 

For  blasting  in  any  soft  material,  such  as  rotten 
or  soft  stone,  where  the  material  is  wanted  broken 
down  in  large  fragments,  a  coarse-grained  powder 
should  be  used.  Where  the  material  is  hard,  or 
where  it  is  to  be  broken  up  fine,  a  fine-grained 
powder  should  be  used.  In  either  case  an  equal 
amount  of  material  will  be  removed,  but  in  the 
latter  instance  the  rock  will  be  shattered  into 
finer  fragments. 

Hard-pressed  powders  and  glazed  powders 
97 


Rock    Excavating    and    Blasting 


burn  slower  than  soft-pressed  powders  of  the 
same  grade  or  unglazed  powders.  Also  hard 
pressed  and  glazed  powders  are  not  affected  by 
moisture  as  readily  as  soft-pressed  or  unglazed 
powders.  Again,  on  account  of  the  greater 
density  of  the  hard-pressed  grades  of  black 
powder,  and  on  account  of  the  smooth  polish 
on  glazed  powders,  these  grades  will  pack  closer 
in  bore  holes  and  cartridges,  consequently  give  a 
greater  explosive  force,  bulk  for  bulk,  than  the 
soft-pressed  powders  or  the  unglazed  powders. 
Therefore,  in  the  selection  of  a  suitable  powder 
for  any  particular  work  these  several  properties 
must  be  taken  into  consideration. 

INITIAL  FORCE  OF  EXPLOSIONS. — The  potassium 
nitrate  in  a  powder  furnishes  the  oxygen  for  the 
combustion  of  the  carbon  and  sulphur,  which  re- 
sults in  the  production  of  a  large  volume  of  heated 
gas.  It  is  the  pressure  of  this  large  volume  of 
gas  which  disrupts  the  rock  in  which  it  is  liber- 
ated, consequently  the  greater  the  volume  of  the 
gas  produced  and  the  tighter  it  is  confined  the 
greater  is  the  rending  or  shattering  force. 

After  a  blast  has  taken  place  the  solid  residue 
remaining  occupies  about  one-third  of  the  original 
volume  or  space,  while  powder  exploded  under 
conditions  similar  to  those  in  practice  yields  from 
175  to  200  volumes  of  gas  at  ordinary  temperature 
and  atmosphere  pressure.  The  solid  products  re- 
sulting from  the  explosion  occupying  slightly  more 
than  one-third  of  the  original  volume  of  the  ex- 

98 


Rock    Excavating    and    Blasting 


plosive,  and  the  gaseous  products  somewhat  less 
than  two-thirds,  gives  the  relative  volume  of  gases 
with  respect  to  the  actual  volume  of  the  hole  they 
occupy  as  from  260  to  300  volumes.  But  we  have 
been  assuming  that  the  expansion  of  the  gas  took 
place  at  ordinary  temperature.  As  a  matter  of 
fact,  however,  there  would  be  a  great  increase  in 
temperature  due  to  the  explosion,  and  the  volume 
of  gas  resulting  would  be  many  times  more  than 
300,  depending  upon  the  nature  of  the  explosive 
used. 

The  temperature  of  combustion  for  most  of  the 
explosives  varies  from  5,000  degrees  Fahrenheit 
to  6,000  degrees  Fahrenheit.  In  blasting  coal 
with  black  powder  the  temperature  of  explosion 
does  not  much  exceed  2,000  degrees  Fahrenheit, 
owing  to  the  slow  combustion  of  the  powder  and 
the  yielding  nature  of  the  coal,  which  shatters  be- 
fore the  maximum  pressure  can  be  reached.  This 
gives  in  coal  blasting  an  expansion  of  about  five 
times  the  gas  produced,  due  to  the  heat  of  the 
explosion. 

If,  then,  the  relative  volume  of  gas  produced  in 
powder  blasting  is  300  volumes,  and  the  expansion 
due  to  heat  equals  five  times,  the  blasting  volume, 
pent  up  in  that  part  of  a  drill  hole  originally 
occupied  by  the  charge  of  powder,  would  be 
300X5=1,500  volumes  of  gas. 

High  explosives,  on  the  other  hand,  produce 
When  exploded  about  1,300  volumes  of  gas  at 
ordinary  temperature,  or  about  16,000  volumes 
at  the  temperature  of  combustion,  giving  a  vol- 

99 


>\      Rock    Excavating    and    Blasting 


ume  ten  times  greater  than  that  of  powder.  This 
is  possible  on  account  of  the  quicker  action  of 
high  explosives,  which  evolves  the  gases  and 
raises  them  in  temperature  before  fissures  in  the 
rock  have  time  to  open. 

Powder  used  in  rock  blasting,  on  account  of 
the  greater  resistance  of  the  rock,  will  create  a 
greater  volume  than  in  coal  blasting.  In  practice 
it  can  be  assumed  that  under  ordinary  condi- 
tions low  explosives  are  capable  of  1,500  expan- 
sions in  blasting  coal,  about  2,000  in  blasting 
rock,  while  high  explosives  are  capable  of  about 
16,000  expansions  under  similar  conditions. 

The  initial  force  of  an  explosion,  or  the  press- 
ure exerted  at  the  instant  the  explosion  takes 
place,  is  proportional  to  the  number  of  expansions 
of  which  the  explosives  are  capable,  and  is  equal 
to  the  atmospheric  pressure  multiplied  by  the 
number  of  expansions. 

Example:  With  the  atmospheric  pressure  14.7 
pounds  per  square  inch,  and  blasting  powder  de- 
veloping 2,000  expansions  in  rock  blasting,  what 
will  be  the  initial  force  of  an  explosion  in  tons 
per  square  inch? 

2,000 
Solution  :       -  "      =U'7  tons  per  Sq"  in* 


MECHANICAL  WORK  OF  AN  EXPLOSION.  —  Theo- 
retically, as  pointed  out  in  the  preceding  para- 
graph, the  mechanical  work  of  which  an  explosive 
is  capable  is  estimated  by  multiplying  the  volume 
of  gas  produced  in  the  explosion  by  the  pressure 

100 


Rock    Excavating    and    Blasting 


of  the  atmosphere.  In  practice,  however,  the 
theoretical  amount  of  work  can  never  be  realized. 
Further,  the  factors  or  conditions  affecting  the 
force  of  an  explosion  are  so  varied  that  seldom 
can  exactly  similar  results  be  obtained  from 
blasts  fired  apparently  under  similar  conditions. 

The  stored  energy  of  an  explosive  is  only  partly 
converted  into  mechanical  work  in  blasting,  some 
of  the  heat  of  combustion  being  lost  by  conduction 
in  the  material  enclosing  the  explosive.  In  case 
the  drill  hole  is  damp  or  wet  or  the  rock  cold  it 
will  decrease  the  available  heat  produced  by  the 
discharge  and  the  power  of  the  explosive.  Further, 
slips,  joints,  cleavage  planes  and  loose  tamping 
affect  the  blast,  as  do  also  the  texture  and  struct- 
ure of  the  rock,  so  that  the  work  to  be  done  by 
a  blast  cannot  be  calculated  definitely  beforehand. 

AMOUNT  OF  EXPLOSIVE  REQUIRED. — As  the  ob- 
ject of  blasting  is  merely  to  shatter  and  dislodge 
the  rock  so  that  it  can  be  easily  removed,  only 
enough  explosive  should  be  used  to  do  the  work. 
When  fragments  are  thrown  more  than  a  few 
yards  by  a  blast,  it  is  generally  evidence  that  too 
large  a  charge  of  explosive  was  used.  Unfor- 
tunately, there  is  no  rule  that  will  apply  in  every 
case  as  to  the  amount  of  powder  necessary  to  use 
in  blasting.  There  is,  however,  a  method  and 
formula  by  means  of  which  the  approximate 
amount  of  explosive  to  be  used  may  be  judged, 
and  the  effect  produced  by  such  a  charge  will 
serve  as  a  guide  to  the  quarryman  in  determining 
whether  to  increase  or  decrease  the  amount. 

101 


Rock    Excavating    and    Blasting 


In  starting  work  on  a  new  operation  select  a 
homogeneous  rock  bench  about  2  feet  wide  and  3 
feet  high,  and  in  the  bench,  far  enough  apart  so 
they  will  not  affect  one  another  by  opening  up 
seams  when  blasted,  drill  several  holes  3  feet  deep, 
and  of  the  standard  diameter  corresponding  to 
the  depth. 

The  holes  are  to  be  drilled  2  feet  back  from  the 
face  of  the  bench,  thus  giving  a  line  of  least  re- 
sistance of  2  feet,  to  a  depth  of  3  feet,  which  is 
the  right  proportion. 

Charge  these  several  holes  with  different 
weights  of  the  explosive  to  be  used,  beginning 
with  a  quantity  too  small  to  affect  rupture,  and 
increasing  by  regular  amounts  to  a  charge  which 
will  be  more  than  sufficient.  Explode  all  these 
charges  separately,  one  at  a  time,  and  select  as 
a  coefficient  for  the  formula  the  amount  of  explo- 
sive producing  the  desired  effect. 

The  coefficient  for  future  work  where  the  line 
of  least  resistance  varies  can  then  be  found  by 
means  of  the  following  rule : 

Rule. — To  find  the  coefficient  for  rock  blasting 
divide  the  effective  charge  of  explosion  used  in 
the  trial  holes  by  the  cube  of  the  line  of  least 
resistance.  The  quotient  will  be  the  coefficient  to 
be  used  in  determining  the  amount  of  powder  to 
be  used. 

Expressed  as  a  formula: 
P 

— =  C 
R* 
102 


Rock    Excavating    and    Blasting 


In  which 

P  =weight  of  powder  in  pounds  and  decimals 
of  pounds. 

R3=cube  of  line  of  least  resistance  in  feet  and 
decimals  of  a  foot. 

C  ^coefficient  for  use  in  determining  amount 
of  powder  required. 

Example. — What  is  the  coefficient  required  for 
determining  the  amount  of  powder  to  be  used,  in 
subsequent  blasts  with  greater  lines  of  least  re- 
sistance, when  in  the  trial  blasts,  with  a  line  of 
least  resistance  of  2  feet,  the  powder  used  was 
1-3  pound? 

Solution. — Substituting  in  the  formula  the 
values  given, 

1-3  pound=.33  pounds,  and  23=2x2X2=8;  then 
P        .33 

—  =  —  =  .04125 
R3         8 

Having  determined  the  coefficient,  it  may  be 
used  to  find  the  charge  of  explosive  required  by 
the  following  rule : 

Rule. — To  find  the  charge  of  explosive  required 
for  blasting  rock,  multiply  the  cube  of  the  line 
of  least  resistance  in  feet  by  the  coefficient  de- 
termined by  trial  blasts. 

Expressed  as  a  formula : 

RS  x  C  =  B 
in  which 

R3—  cube  of  line  of  least  resistance. 

C  =  coefficient  obtained  as  explained  above. 

B  =  charge  of  explosive  required. 
103 


>\      Rock    Excavating    and    Blasting 


Example. — What  weight  of  powder  will  be  re- 
quired to  blast  rock  in  which  the  line  of  least  re- 
sistance is  8  feet,  and  the  coefficient  .04125? 

Solution.— R3  =  8X8X8  =  512.  Coefficient  = 
.04125.  Substituting  these  volumes  in  the  form- 
ula: 

R3  C  =  512  X  .04125  =  21.12  pounds  of  pow- 
der. (Answer.) 

In  the  foregoing  example  it  must  be  remem- 
bered all  the  qualities  were  assumed,  so  that  the 
result  obtained  in  the  answer  does  not  necessarily 
represent  the  quantity  that  would  be  found  in  the 
application  of  the  rule  and  formula  in  practice. 
The  example  is  given  and  worked  out  to  show  how 
the  rule  and  formula  are  applied.  The  main  thing 
is  to  find  the  right  coefficient,  for  naturally  this 
will  vary  with  the  kind  and  quality  of  the  rock,  a 
larger  charge  being  required  for  granite  than 
would  be  needed  for  limestone  or  sandstone,  while 
at  the  same  time  a  smaller  charge  would  be  re- 
quired for  a  soft  granite  than  for  a  hard  one, 
which  would  occasion  different  coefficients  for 
these  various  materials. 

The  quantity  of  explosive  determined  in  the 
foregoing  manner  is  for  rock  with  two  free  faces. 
In  blasting  where  three  free  faces  are  exposed 
only  two-thirds  of  the  calculated  charge  need  be 
used.  In  blasting  where  four  faces  are  exposed 
only  one-half  the  calculated  amount  need  be  em- 
ployed. When  five  faces  only  two-fifths  the 
amount,  and  when  all  six  sides,  as  in  the  case  of 
large  blocks,  are  exposed  only  one-quarter  of  the 
calculated  charge  will  be  required. 

104 


Rock    Excavating    and    Blasting 


When  the  quantity  of  explosive  to  use  has  been 
determined  the  size  of  drill  hole  that  will  hold 
the  amount,  while  at  the  same  time  occupying  in 
the  bore  hole  a  depth  or  distance  equal  to  only 
twelve  times  the  diameter,  can  be  found  in  Table 
IX.  This  table  was  compiled  from  the  formula 

C  =  .3396gd3 
in  which 

C  =  weight  of  charge  of  explosive  in  pounds. 

g  =  specified  gravity  of  explosive. 

d  =  diameter  of  hole  in  inches. 

TABLE  IX. 
Size  of  Drill  Holes  for  Different  Weights  of  Explosives. 


Name  of  Explosive 

Specified 
Gravity 
of  Ex- 
plosive 
G 

Diameter  of  Holes  in  Inches 

% 

% 

1 

lX/8 

1% 

1H 

1000 
1120 
1160 
1.550 
1.550 
1.600 

.143 
.160 
•  166 
.222 
.222 
-229 

.228 
-258 
264 
352 
352 
363 

•340 
380 
.394 
526 
.526 
543 

480 
.541 
561 
-749 
.749 
773 

•664 
.742 
.769 
1.027 
1027 
1060 

•880 
.988 
1-024 
1-367 
1-367 
1060 

Ardeer  powder   
Blasting  gelatine  
Gelatine  dynamite  

yn 

Name  of  Explosive 

Specified 
Gravity 
of  Ex- 
plosive 
G 

Diameter  of  Holes  in  Inches 

IK 

IX 

1% 

1* 

2 

2K 

2% 

Blasting  powder-  •  • 
Carbonite  
Ardeer  powder    
Blasting  gelatine  .    .  - 
Gelatine  dynamite     .  . 

1.000 
1.120 
1160 
1-550 
1.550 
1600 

1148 
1.280 
1330 
1-775 
1-775 
1833 

1.459 
1-630 
1-690 
2256 
2.256 
2.329 

1-822 
2036 
2160 
2819 
2819 
2910 

2-240 
2-505 
2597 
3467 
3.467 
3579 

2720 
3-040 
3-151 
4-211 
4.211 
4347 

3872 
4-328 
4488 
5.991 
5991 
6.184 

5-312 
5-936 
6.152 
8218 
8218 
8-480 

*Daw. 

105 


Rock    Excavating    and    Blasting 


It  will  be  observed  that  a  2-inch  drill  hole  will 
hold  only  2.720  pounds  of  blasting  powder  when 
properly  charged,  but  that  by  changing  from  2 
inch  to  21/2  inch  that  charge  can  be  almost 
doubled.  The  table  does  not  give  the  size  of  hole 
for  larger  drill  than  2y%  inches,  which  corresponds 
to  a  charge  of  blasting  powder  of  5.3  pounds. 
This  is  a  sufficiently  large  charge  for  ordinary 
building  practice,  although  in  large  engineering 
works  away  from  habitations  as  high  as  twenty 
pounds  in  a  bore  hole  are  used,  and  from  18  to 
20  of  such  charges  fired  simultaneously.  In  works 
of  that  size  it  is  found  that  in  soft  rock  like  lime- 
stone about  two  cubic  yards  of  rock  can  be  ex- 
cavated for  each  lineal  foot  of  hole  drilled,  and 
that  each  %  pounds  of  powder  brings  down  about 
one  cubic  yard  of  rock. 

When  a  blast  is  fired  the  workmen  can  judge 
whether  or  not  there  has  been  enough,  too  much 
or  the  right  amount  of  explosive  used.  If  the 
right  amount  of  explosive  is  used  there  will  be  a 
deep  boom  and  the  rock  will  not  be  thrown  with 
great  force  for  any  distance  nor  will  it  be  badly 
shattered.  If  there  was  too  much  powder  used 
there  will  be  a  sharp  report  and  the  blast  will 
throw  the  rock  a  considerable  distance,  shattering 
it  badly.  If  not  enough  explosive  is  used,  of 
course,  the  rock  will  not  be  broken  down  in  the 
right-sized  fragments,  as  it  should  be.  If  too 
small  a  charge  is  used  to  break  the  rock  the  tamp- 
ing will  be  blown  out  from  the  drill  hole,  just  as 
a  bullet  is  shot  from  a  gun. 

106 


CHAPTER  X. 


CHARGING  DRILL  HOLES  WITH  POWDER. 


ARTRIDGES  AND  TAMPING  MATER- 
IAL. —  In  open-cut  work  where  the 
drill  holes  are  dry  and  slope  down- 
ward from  the  mouth,  blasting  pow- 
der can  be  poured  into  the  hoie  and 
tamped.  If  the  hole  is  sloped  upward,  however, 
the  powder  cannot  be  poured  in  loose,  but  must 
first  be  enclosed  in  cartridges,  which  are  usually 
cylinders  of  Manila  paper,  and  these  cartridges 
can  be  tamped  into  the  drill  hole.  In  damp  holes, 
likewise,  the  powder  should  be  confined  in  cart- 
ridges to  prevent  it  from  losing  its  effectiveness 
by  becoming  damp  or  wet.  Bore  holes  under- 
ground should  never  be  loaded  with  loose  powder 
on  account  of  the  danger  of  dust  from  the  powder 
coming  in  contact  with  lights  and  carrying  the 
flames  to  the  main  body  of  powder,  thus  causing 
an  explosion. 

The  cartridges  for  use  in  blasting  can  be  made 
by  rolling  paper  around  a  wooden  cartridge  bar 
of  a  slightly  smaller  diameter  than  the  drill  hole. 
The  loose  edges  of  the  paper  are  stuck  down  by 

107 


Rock    Excavating    and    Blasting 


means  of  miner's  soap,  one  end  of  the  paper  is 
folded  over  to  close  the  end  of  the  cartridge,  and 
the  stick  when  removed  leaves  a  paper  cylinder. 
When  the  cylinder  is  filled  with  powder,  the  cart- 
ridge is  completed  by  folding  down  the  other 
end. 

A  uniform  and  compact  tamping  is  essential 
with  the  use  of  black  powder.  For  tamping  black 
powder  the  material  used  should  be  free  from 
small  pieces  of  stone  or  other  hard  substances 
which  might  produce  sparks  or  damage  the  fuse, 
consequently  stone  dust  and  coal  dust  are  not  con- 
sidered suitable  tamping,  although  for  want  of 
better  materials  they  are  sometimes  used.  The 
best  material  for  tamping  is  moist  clay.  In  holes 
having  anything  but  a  downward  slant  the  tamp- 
ing material  is  best  wrapped  in  short  paper  cart- 
ridges. When  loose  powder  is  used  a  wad  of 
paper  should  be  tamped  between  the  powder  and 
the  wet  clay. 

In  tamping,  if  the  hole  is  dry,  the  cartridges 
may  be  tamped  hard  enough  to  break  the  paper 
so  the  powder  will  pack  close  and  fill  all  crevices — 
for  the  closer  the  powder  is  packed  in  the  hole 
the  greater  will  be  the  effect  produced  by  the 
blast.  If  the  hole  is  drilled  in  seamy  rock  a  ball 
of  clay  may  first  be  put  into  the  hole  and  a  bar 
driven  into  it  to  spread  out  and  fill  the  seams 
and  crevices.  If  these  crevices  are  not  filled  the 
gases  formed  by  the  explosion  will  escape  through 
them  and  part  of  the  force  of  the  blast  will  be 
lost.  In  wet  drill  holes  the  cartridges  should  be 

108 


Rock    Excavating    and    Blasting 


well  coated  with  miner's  soap  and  the  filling  not 
tamped  hard  enough  to  break  the  paper. 

DEPTH  OF  TAMPING.  —  In  deep  drill  holes  it  is 
never  necessary  to  tamp  the  hole  full,  only  suffi- 
cient tamping  being  necessary  to  prevent  a  blow- 
out or  to  prevent  yielding  before  the  full  force  of 
the  explosion  is  reached.  With  dynamite  and 
other  high  explosives  which  develop  their  full 
power  instantaneously,  less  tamping  is  required 
than  with  powder,  for  the  reason  that  with  the 
high  explosives  the  shock  is  delivered  on  the  sides 
of  the  chamber  with  sufficient  force  to  burst  the 
rock  before  it  has  time  to  affect  the  tamping. 
With  high  explosives  very  light  tampings  are 
sometimes  used,  as,  for  instance,  filling  the  drill 
hole  with  water  or  filling  the  hole  a  few  inches 
with  sand  or  fine  dirt,  while  for  powder  blasting 
considerable  tamping  must  be  used,  the  depth  of 
tamping  depending  on  the  diameter  of  hole.  For 
1-inch  holes  the  very  least  tamping  that  will  hold 
is  17  inches  ;  in  a  2-inch  hole,  18  inches  of  tamping  ; 
and  in  a  3-inch  hole  not  less  than  20  inches  ol 
tamping.  These  values  are  the  minimum,  it  must 
be  remembered,  and  in  actual  practice  not  less 
than  2  feet  should  be  used  for  any  size,  while 
even  deeper  tampings  will  prove  safer. 

METHOD  OF  CHARGING  A  DRILL  HOLE.  —  In  Fig. 
48  is  shown  how  a  drill  hole  is  charged  with  pow- 
der, tamped  and  made  ready  to  fire  with  a  fuse. 
The  fuse,  it  will  be  noticed,  is  extended  to  the 

109 


Rock    Excavating    and    Blasting" 


center  of  the  powder  cartridge  and  where  it  leaves 
the  top  end  of  the  cartridge  is  offset  to  one  side 
of  the  drill  hole  to  make  way  for  the  tamping. 
The  tamping  bar  has  a  groove  at  one  side  so  it 
will  not  cut  or  strip  the  fuse,  or  needle  when  a 


Fig.  48. 
Method  of  Charging  Drill  Hole. 

110 


Rock    Excavating    and    Blasting 


squib  needle  is  used,  and  at  the  same  time  will 
tamp  the  filling  well  around  the  fuse  or  needle. 
Tamping  rods  having  metal  parts  should  never  be 
used  on  account  of  the  danger  of  striking  sparks 
when  tamping.  When  loose  powder  is  poured  in 
the  hole  it  is  of  the  greatest  importance  to  use  a 
wooden  tamping  rod,  as  an  iron  rod  coming  in 
contact  with  stone  or  pyrites  is  liable  to  spark  and 
cause  a  premature  explosion.  Whenever  a  metal 
tamping  rod  is  used,  it  should  be  either  copper  or 
brass,  never  iron  or  steel. 

In  filling  the  drill  hole  the  tamping  is  put  in 
and  tamped  little  by  little,  the  first  few  inches 
being  rammed  hard  and  the  remainder  only  pack- 
ed sufficiently  tight  to  keep  its  shape  and  leave 
open  the  needle  hole  when  a  squibbing  needle  is 
used. 

SQUIBBING.  —  Charging  with  a  needle  and  fir- 
ing by  means  of  a  squib  is  practised  rather  ex- 
tensively, particularly  in  mines,  but  the  operation 
is  rather  dangerous  and  requires  careful  manipu- 
lation. In  this  method  a  rod  of  metal  called  a 
needle,  about  14  inch  in  diameter  and  pointed  at 
one  end,  is  placed  along  the  side  of  the  bore  hole, 
the  powder  placed  in  position,  pressed  down,  the 
hole  tamped  and  the  needle  carefully  withdrawn. 
When  the  powder  is  in  a  cartridge,  the  cartridge 
is  first  inserted  in  the  bore  hole  and  the  needle 
then  placed  in  position,  with  the  point  piercing  the 
cartridge  a  few  inches.  The  withdrawal  of  the 
needle  then  leaves  a  channel  down  one  side  of  the 

111 


Rock    Excavating    and    Blasting 


tamping  and  into  the  center  of  the  powder  in  the 
cartridge,  into  which  the  squib  is  inserted. 

A  squib  is  a  small  paper  tube  or  straw  that  is 
filled  with  a  quick  powder  and  has  a  slow  match 
attached  to  one  end.  The  burning  of  the  slow 
match  gives  the  workman  time  to  get  away  after 
lighting  it  and  before  the  flame  reaches  the  pow- 
der. When  this  quick  powder  in  the  paper  tube 
is  fired  it  shoots  like  a  rocket  back  into  the  blast- 
ing powder  through  the  hole  in  the  tamping  left 
by  the  withdrawal  of  the  needle. 

In  squib  firing  a  metal  needle  is  required,  but 
this  metal  should  be  copper  or  some  alloy  like 
brass.  It  should  never  be  of  iron  or  steel  for  the 
same  reason  given  for  not  using  a  steel  or  iron 
tamping  rod. 

USES  FOR  POWDERS  AND  DYNAMITES. — Black 
powders  are  generally  favored  for  use  in  coal 
mines,  building-stone  quarries  or  other  places 
where  the  material  is  to  be  taken  out  without  too 
much  shattering.  Also  for  blasting  in  soft  ma- 
terials where  all  classes  of  high  explosives  are  too 
quick  in  their  action  to  utilize  their  entire 
strength.  The  great  advantage  of  powder  in  these 
classes  of  work  is  that  it  exerts  a  strong  push 
upon  the  material  to  be  removed,  not  a  quick, 
sharp,  shattering  blow,  characteristic  of  high  ex- 
plosives. 

It  must  be  remembered,  however,  that  dynamite 
is  now  made  in  nine  or  ten  different  grades,  some 
slow  acting,  others  quick  acting,  some  full 

112 


Rock    Excavating    and    Blasting 


strength,  others  of  less  strength,  so  that  dynamite 
can  be  used  for  almost  every  purpose  that  black 
powder  is  suitable  for,  and  for  many  purposes 
for  which  powder  would  be  unfit. 

TESTS  OF  BLASTING  POWDER. — The  only  tests  of 
gunpowder  that  need  be  made  by  workmen  or  the 
superintendent  on  the  premises  are  some  simple 
ones  to  determine  whether  or  not  the  powder  is 
dry  and  in  good,  usable  condition.  If  the  powder 
has  absorbed  moisture  enough  to  make  it  wet  or 
damp,  it  should  not  be  used  until  dried.  One  way 
to  test  for  moisture  is  to  rub  the  grains  of  powder 
on  a  piece  of  clean  white  paper.  If  the  paper  be- 
comes blackened  the  powder  is  moist,  while  if  not 
discolored  no  moisture  is  present. 

Another  method  is  the  ignition  test.  If  a  small 
quantity  of  good,  dry  powder  is  ignited  on  a  sheet 
of  dry  paper  it  will  flash  up  instantly  without 
burning  the  paper  or  discoloring  it  to  any  great 
extent.  Burning  of  the  paper  usually  indicates 
the  presence  of  moisture.  Black  spots  left  on 
the  paper  after  flashing  the  powder  indicate  an 
excess  of  charcoal  or  an  imperfect  mixing  of  the 
ingredients,  usually  the  former,  as  with  the  ma- 
chinery used  in  making  powder  the  ingredients 
are  well  mixed  together.  Yellow  spots  on  the 
paper  indicate  an  excess  of  sulphur  in  the  powder. 

These  tests  at  their  best,  while  simple  and  easily 
made,  give  only  a  rough  approximate  idea  of  the 
quality  or  condition  of  the  powder.  At  all  events, 
if  sufficient  heat  must  be  applied  to  the  powder 

113 


Rock    Excavating    and    Blasting 


in  testing  to  ignite  the  paper,  it  is  pretty  conclu- 
sive evidence  that  the  powder  is  damp  and  not  fit 
for  use  without  drying. 

DRYING  BLASTING  POWDER. — Don't  use  wet 
blasting  powder.  If  the  powder  is  only  damp  it 
can  be  dried,  thereby  making  it  suitable  for  use. 
The  only  way  to  dry  damp  blasting  powder  is  to 
spread  it  out  in  the  hot  sun  on  a  dry  day  and  in 
a  protected  place  where  the  wind  cannot  blow  it 
away.  The  powder  must  be  spread  out  in  a  thin 
layer  and  on  a  platform  raised  from  the  ground 
so  it  cannot  absorb  moisture  as  it  is  given  off. 

Powder  should  never  be  dried  on  a  stove  or 
near  a  fire,  whether  in  the  powder  keg  or  loose, 
as  there  is  liable  to  be  a  flash  or  explosion  if  it 
becomes  overheated.  The  best  way  is  to  avoid  the 
use  of  blasting  powder  if  there  is  danger  of  it 
becoming  damp  or  wet,  and  use  a  suitable  grade 
of  dynamite. 

HANDLING  BLASTING  POWDER  UNDERGROUND. — 
Too  great  care  cannot  be  exercised  in  the  handling 
of  blasting  powder  underground  in  tunnels  or 
shafts.  Underground  bore  holes  should  never  be 
loaded  with  powder  unless  the  powder  is  made  up 
into  cartridges.  The  cartridges  had  better  be 
made  up  in  daylight  on  the  surface  and  carried 
down  in  that  way.  Under  no  condition  should  a 
light,  unless  a  safety  lamp,  be  permitted  near  an 
open  keg  of  powder,  and  if  necessary  to  make  up 
powder  cartridges  underground  the  light  should 

114 


Rock    Excavating    and    Blasting 


be  kept  well  away  from  the  powder  and  to  the 
windward  side  of  it.  If  the  light  were  on  the 
"lee"  side  of  the  keg,  powder  dust  from  the  loading 
might  communicate  with  the  light,  thereby  carry- 
ing the  flame  to  the  main  body  of  the  powder  and 
exploding  it.  This  is  the  reason  that  loose  pow- 
der should  not  be  used  for  charging  bore  holes 
underground.  Trails  of  powder  spilled  on  the 
ground  or  powder  dust  in  the  air  might  lead  to 
a  premature  blast  or  an  explosion  of  the  powder 
in  the  keg. 

TAMPING  BAGS. — No  bore  hole  can  be  properly 
charged  with  loose  powder  unless  the  bore  hole 
points  down.  In  tunnel  driving  and  other  inside 
and  outside  work,  however,  many  of  the  drill 
holes  point  upward,  and  to  properly  charge  them 
with  powder  the  powder  must  first  be  made  up 
in  the  form  of  a  cartridge.  In  tamping  bore  holes 
that  point  upward  it  is  likewise  practically  im- 
possible to  get  loose  material  to  stay  in  the  hole 
as  it  should,  and  in  practice  tamping  bags  are 
made  to  hold  the  tamping  material.  Tamping 
bags  and  cartridges  are  made  in  the  same  way 
and  same  size  and  may  be  made  by  the  workman 
himself  as  previously  explained,  or  can  be  had 
with  other  blasting  supplies. 

The  size,  weight  and  other  information  about 
stock  tamping  bags  can  be  found  in  Table  X. 

Blasting  powder  weighs  approximately  the 
same  as  water,  which  is  29.2  cubic  inches  to  the 
pound.  For  convenience  in  calculating,  30  cubic 

115 


Rock    Excavating    and    Blasting 


TABLE  X. 
Size,  Number  and  Weights  of  Tamping  Bags. 


Size 

Size  in 

Number 

Shipping 
Weight 

Approximate 
Weight  One 

Number 

Inches 

in  Bale 

per 

Powder  Bag 

Bale 

Will  Hold 

A 

1      x8 

5   M 

32  Pounds 

3     Ounces 

B 

IK  x8 

5   M 

33 

5 

C 

IK  xlO 

5   M 

35 

6K 

D 

!Kxl2 

5  M 

40 

1% 

E 

IK  x8 

5  M 

35 

7K 

F 

IKxlO 

5  M 

40 

9K 

G 

!Kxl2 

5  M 

57 

11 

H 

IK  x  16 

5  M 

105 

15 

inches  of  powder  is  often  assumed  as  weighing 
a  pound.  This  gives  to  a  cubic  inch  of  powder  an 
approximate  weight  of  .53  ounces.  These  figures 
are,  of  course,  only  approximate,  as  the  weight  of 
powder  in  bulk  depends  on  the  size  of  the  grains 
and  how  closely  the  grains  are  packed.  The  in- 
dividual grains  themselves  likewise  differ  in 
weight,  varying  in  specific  gravity  from  1.5  to 
1.85. 


116 


CHAPTER  XL 


HIGH  EXPLOSIVES. 


DYNAMITE. 

ITROGLYCERINE.—  There  are  a 
number  of  high  explosives  used  for 
different  purposes,  but  so  far  as  or- 
dinary rock  blasting  is  concerned 
dynamite  and  blasting  gelatine  are 
the  only  ones  that  need  be  considered  in  detail. 
It  will  be  well,  however,  to  explain  the  nature  of 
nitroglycerine,  as  this  will  help  to  a  better  under- 
standing of  the  nature  of  dynamite,  while  gun 
cotton  will  also  be  considered  as  one  of  the  active 
principles  in  all  blasting  gelatines. 

Nitroglycerine  is  a  mixture  of  nitric  acid,  sul- 
phuric acid  and  glycerine.  The  glycerine  used  is 
the  pure  glycerine  of  commerce,  a  heavy,  oily 
liquid  resembling  syrup  and  known  as  the  sweet 
principle  of  oils.  It  is  obtained  by  the  decomposi- 
tion of  vegetable  or  animal  fats  or  fixed  oils.  In 
the  manufacture  of  nitroglycerine  three  parts  of 
strong  nitric  acid  are  mixed  with  five  parts  of 
concentrated  sulphuric  acid,  and  after  this  mix- 
ture, which  has  become  heated  by  the  process, 

117 


Rock    Excavating    and    Blasting  ^ 


cools  off,  1  to  1.15  parts  of  glycerine  are  slowly 
and  gradually  added,  the  mixture  being  stirred  all 
the  while.  In  the  manufacture  of  nitroglycerine 
in  dynamite  mills,  compressed  air  is  generally 
used  for  mixing  the  ingredients,  and  every  pre- 
caution is  taken  to  prevent  the  mixture  from  heat- 
ing. 

After  the  nitroglycerine  has  been  mixed  it  is 
poured  into  five  or  six  times  its  bulk  of  cold  water, 
where  it  sinks  to  the  bottom  as  a  heavy,  oily  liquid 
of  a  yellowish  tint.  The  color  is  due  to  impurities 
in  the  ingredients,  absolutely  pure  nitroglycerine 
being  clear  and  transparent. 

PROPERTIES  OF  NITROGLYCERINE. — At  ordinary 
temperature  nitroglycerine  is  an  oily  liquid,  and 
must  be  confined  in  a  bottle  or  like  receptacle.  It 
does  not  mix  well  with  warm  water,  and  seems 
to  be  unaffected  by  cold  water,  which  makes  solid 
explosives  made  of  this  mixture  suitable  for  use  in 
damp  places  and  under  water. 

Nitroglycerine  has  a  sweet,  pungent  taste,  is 
an  active  poison,  and  produces  in  those  unaccus- 
tomed to  handle  it  nausea,  faintness  and  severe 
headaches.  Persons  of  a  nervous  temperament 
are  more  easily  affected  than  others,  but  become 
accustomed  to  handling  it  without  noticeable  ef- 
fect when  made  up  into  dynamite  or  like  com- 
pounds. 

In  the  liquid  state,  when  confined,  nitroglycerine 
is  very  sensitive  and  a  slight  concussion  or  jar 
is  liable  to  explode  it.  This  unstability  makes 

118 


^V>\      Rock    Excavating    and    Blasting 
^^^•••^^••^••^^^••••••••••^•^^••••••••••^^^^•^•^ 

nitroglycerine  dangerous  to  store  and  handle,  con- 
sequently it  is  not  used  extensively  in  liquid  con- 
dition. 

When  frozen,  nitroglycerine  is  less  sensitive  to 
concussion  than  when  in  the  liquid  state,  but  it  is 
still  dangerous  to  handle  and  the  process  of  thaw- 
ing is  both  difficult  and  dangerous.  The  explosive, 
furthermore,  loses  some  of  its  force  after  freezing, 
so  that  all  told  little  if  anything  is  gained  by 
keeping  it  in  the  solid  condition.  Freshly  made 
nitroglycerine  freezes  at  55  degrees  F.,  while  puri- 
fied nitroglycerine  freezes  to  a  white,  crystalline 
mass  at  36  degrees  F. 

The  firing  point  of  nitroglycerine  is  356  degrees 
Fahrenheit,  a  comparatively  low  temperature, 
equal  only  to  that  of  steam  under  a  pressure  of 
132  pounds  per  square  inch,  but  it  decomposes  at 
a  lower  heat.  When  unconfined,  nitroglycerine 
will  burn,  but  a  spark  will  not  explode  it,  a  con- 
cussion or  detonation  being  necessary  to  produce 
an  explosion. 

Outside  of  shooting  oil  wells,  blowing  safes  and 
for  a  few  purposes  like  that  nitroglycerine  is  not 
extensively  used  in  its  free  state.  Its  interest  to 
us  here  lies  in  the  fact  that  it  is  the  active  agent 
in  all  forms  of  dynamite,  really  is  still  nitroglyce- 
rine when  made  into  dynamite,  but  is  thus  made 
comparatively  safe  to  store  and  handle. 

DYNAMITE. — Dynamite  is  simply  nitroglycerine 
absorbed  by  some  absorbent  material  called  a 
dope.  If  the  dope  is  merely  an  absorbent  for  the 

119 


Rock    Excavating    and    Bl  a s  t i n g 


nitroglycerine  and  does  not  add  anything  to  the 
explosive  character  of  the  mixture  it  is  said  to  be 
inactive.  If,  on  the  other  hand,  the  dope  is  of 
such  a  material  or  composition  that  when  the  ex- 
plosion takes  place  the  dope  also  ignites  or  ex- 
plodes, thereby  adding  to  the  force  of  the  initial 
explosion,  the  dope  is  said  to  be  active.  Strictly 
speaking,  the  term  dynamite  is  applied  only  to 
those  nitroglycerine  explosives  which  have  an  in- 
active dope,  and  special  trade  names  are  given 
to  those  mixtures  in  which  the  dope  is  active. 
Ordinary  dynamite,  also  dynamites  with  active 
bases,  possess  the  advantages  over  nitroglycerine 
not  only  that  they  are  less  sensitive  and  can  there- 
fore be  more  easily  and  safely  handled,  but  they 
can  further  be  made  in  various  degrees  of 
strength  and  put  up  in  packages  for  convenient 
handling. 

DYNAMITE  WITH  AN  INACTIVE  BASE. — Dyna- 
mites with  inactive  bases  have  been  made  with 
such  inert  dopes  as  infusorial  earth,  magnesium 
carbonate,  sawdust  and  charcoal.  Of  all  the  fore- 
going materials  infusorial  earth  makes  the  best 
dope,  as  this  earth  is  very  porous  and  when  care- 
fully prepared  will  absorb  75  per  cent,  of  nitro- 
glycerine. In  America,  however,  very  little  dyna- 
mite is  made  with  infusorial  earth,  charcoal  or 
any  of  the  other  dopes  enumerated  above,  for  the 
reason  that  cheaper  dopes  of  equal  safety  can  be 
had  in  the  form  of  wood  pulp.  The  wood  pulp  is 
usually  mixed  with  sodium  nitrate,  which  fur- 

120 


Rock    Excavatin g    and    Blasting 


nishes  oxygen  for  burning  the  wood  pulp  when 
the  dynamite  is  exploded.  When  a  silicious  dope 
like  infusorial  earth  is  used,  on  the  other  hand, 
it  is  inert,  acts  merely  as  an  absorbent,  and  leaves 
a  residue  when  the  dynamite  is  exploded.  Dyna- 
mite having  an  inactive  base  and  containing  less 
than  30  per  cent,  of  nitroglycerine  cannot  be  ex- 
ploded. 

DYNAMITE  WITH  AN  ACTIVE  BASE. — As  ordin- 
ary dynamite  cannot  be  exploded  when  it  contains 
less  than  30  per  cent,  of  nitroglycerine,  that  is 
the  lowest  possible  amount  that  can  be  used,  and 
the  force  of  the  explosion  cannot  be  regulated  be- 
low that  limit.  The  force  of  an  explosion  from 
that  minimum  limit  upward,  however,  can  be  reg- 
ulated by  varying  the  amount  of  nitroglycerine 
the  dynamite  contains.  That  is  the  reason  or- 
dinary dynamite  is  not  suitable  for  blasting  coal, 
rock  for  building  purposes,  or  for  other  purposes 
where  shattering  is  not  desired,  while  at  the  same 
time  special  dynamites  with  active  bases  can 
sometimes  be  used  for  those  purposes  to  good  ad- 
vantage. 

If,  instead  of  the  inactive  base,  some  combusti- 
ble or  explosive  substance  be  used  as  an  absorbing 
dope  and  the  proportion  of  nitroglycerine  can  be 
reduced  below  30  per  cent.,  it  will  explode,  and 
the  force  of  the  explosion  will  be  less  than  that 
from  the  weakest  common  dynamite.  On  the 
other  hand,  by  retaining  the  same  percentages  of 
nitroglycerine  and  using  an  active  base  the  force 

121 


Rock    Excavating    and    Blasting 


of  an   explosion  can  be  increased  beyond  that 
which  the  nitroglycerine  alone  produces. 

STRENGTH  OF  DYNAMITE. — The  strength  of  all 
high  explosives  is  based  on  their  execution,  com- 
paring them  with  ordinary  dynamite  of  known 
percentage.  For  instance,  much  of  the  dynamite 
now  sold  has  an  active  base,  but  is  classed  as  an 
ordinary  dynamite  so  far  as  strength  is  concern- 
ed. It  is  rated  as  40,  50  and  60  per  cent,  dyna- 
mite, but  this  does  not  mean  it  contains  that  per- 
centage of  nitroglycerine,  but  that  it  has  an  ex- 
plosive force  equal  to  40,  50  or  60  per  cent,  com- 
mon dynamite.  Common  dynamite,  which  is  the 
standard  of  comparison,  is  rated  according  to  the 
amount  of  nitroglycerine  it  actually  contains,  and 
a  40  per  cent,  common  dynamite  means  that  it 
possesses  40  per  cent,  of  nitroglycerine. 

The  strength,  or  disruptive  force,  of  special 
dynamites  is  due  to  the  active  ingredients  form- 
ing the  base  as  well  as  to  the  nitroglycerine. 
These  ingredients  differ  in  the  fumes  they  evolve, 
water-resisting  properties  and  resistance  to 
freezing — consequently  it  is  necessary  to  use  dif- 
ferent grades  for  different  works,  a  non-gas- 
forming  dynamite  for  tunnel  or  shaft  work,  a 
frost-resisting  brand  for  outdoor  work  and  cold 
weather,  and  a  dynamite  that  will  not  be  dam- 
aged by  water  for  blasting  in  wet  places. 

APPEARANCE  OF  DYNAMITE. — Dynamite  looks 
something  like  fine  sawdust  slightly  dampened, 
but  varying  in  color  from  black,  brown,  yellow, 

122 


Rock    Excavating    and    Blasting 


gray  to  almost  white,  depending  on  the  ingredi- 
ents used  for  the  dope.  For  use  in  blasting,  dyna- 
mite is  made  up  into  cartridges  as  shown  in  Fig- 
ure 49.  The  cartridge  wrappers  are  made  of 


Fig.  49. 
Cartridge  of  Dynamite. 

cylinders  of  paraffined  brown  paper,  carefully 
folded  down  or  crimped  at  the  ends  so  that  none 
of  the  contents  can  run  out. 

SIZE  OF  DYNAMITE  CARTRIDGES. — Dynamite 
cartridges  are  made  of  such  diameters  that  they 
will  enter  their  complementary  bore  holes,  if  of 
standard  size,  without  forcing  them.  They  are 
made  in  sizes  from  %  incn  to  2  inches  in  diameter, 
and  in  length  of  8  inches.  The  standard  stock 
sizes  and  approximate  weights  of  dynamite  cart- 
ridges can  be  found  in  Table  XI. 

TABLE  XI. 
Sizes  and  Weights  of  Dynamite  Cartridges. 


Diameter  of  Cartridge 

Length  of  Cartridge 

Approximate  Weight 
of  Dynamite 

%  Inches 

8  Inches 

2  Ounces 

1 

8 

4 

1H 

8 

5 

IK 

8 

6 

IK 

8 

9 

m 

8 

12 

2 

8 

1  Pound 

123 


@^\>\      Rock    Excavating    and    Blasting 

Dynamite  is  shipped  in  twenty-five  and  fifty- 
pound  wooden  boxes,  lined  with  paraffined  paper 
and  packed  with  sawdust. 

PROPERTIES  OF  DYNAMITE. — Dynamite  is  rather 
plastic,  which  favors  its  being  charged  in  a  drill 
hole.  In  spite  of  the  fact  that  glycerine  is  an  oil, 
dynamite  is  not  what  would  be  called  greasy.  The 
specific  gravity  of  dynamite  depends  some  on  its 
dope.  Ordinarily,  the  specific  gravity  is  about 
1.15,  which  being  heavier  than  water  favors  it 
when  used  for  submarine  blasting.  Dynamite  has 
the  physical  qualities  of  nitro-glycerine  so  far  as 
explosive  power  is  concerned,  and  is  equally  poi- 
sonous to  those  unaccustomed  to  handle  it.  Like 
nitroglycerine,  dynamite  has  a  firing  point  of  356 
degrees  Fahrenheit,  at  which  temperature  it  will 
either  burn  or  explode.  If  free  from  gas  or  pres- 
sure it  will  burn,  but  if  jarred,  even  when  loose 
and  unconfined,  may  explode. 

Ordinary  dynamite  freezes  at  a  temperature 
of  about  43  degrees  Fahrenheit  and  becomes  in- 
sensitive at  from  45  to  50  degrees  Fahrenheit. 
When  completely  frozen  dynamite  is  hard  and 
rigid.  This  condition  is  easily  recognized,  but  it 
requires  a  careful  examination  to  determine 
whether  or  not  it  is  only  partly  frozen  or  chilled. 
Dynamite  will  not  do  good  work  if  chilled,  and 
when  solidly  frozen  it  is  difficult  or  impossible  to 
explode  it,  or  if  it  does  explode  the  detonation  at 
best  is  only  partial.  Care  should  be  taken,  there- 
fore, to  see  that  the  explosive  is  thoroughly  thaw- 

124 


Rock    Excavating    and    Blasting 


ed  in  cold  weather  before  using.  It  is  dangerous 
to  cut,  break  or  ram  a  frozen  dynamite  cartridge, 
as  part  of  the  cartridge  might  be  in  a  thawed  con- 
dition and  the  nitroglycerine  crystals  explode. 

The  sensitiveness  of  dynamite  to  blows  or 
shocks  increases  very  rapidly  with  rise  of  temper- 
ature, as  would  be  expected,  as  that  is  a  condition 
common  to  nitroglycerine,  from  which  it  is  made. 

In  the  foregoing  paragraphs  the  properties  of 
ordinary  dynamite  are  pointed  out.  It  will  be 
well  for  the  quarryman  to  remember,  however, 
that  there  are  special  makes  of  high  explosives 
which  differ  greatly  in  behavior  from  ordinary 
dynamite,  while  having  the  same  explosive  force. 
Monobel  and  Judson  powder  R.  R.  P.,  for  instance, 
freeze  at  the  same  temperature  as  dynamite,  but 
if  a  suitable  detonator  be  used  they  can  be  prop- 
erly exploded  even  when  frozen.  The  Arctic 
brand  of  dynamite,  on  the  other  hand,  does  not 
freeze  at  all,  and  the  Red  Cross  grades  do  not 
freeze  until  water  freezes,  at  a  temperature  of  32 
degrees  Fahrenheit.  It  would  follow  from  the 
foregoing  that  high  explosives  differ  widely  in 
their  character,  and  it  is  of  the  greatest  import- 
ance to  select  a  grade  best  adapted  for  the  work 
to  be  done.  Besides  the  different  conditions  under 
which  various  grades  of  dynamite  can  be  used, 
each  kind  of  high  explosive,  except  blasting  gela- 
tine, is  made  in  different  strengths,  and  each 
strength  is  put  up  in  cartridges  of  various  diam- 
eters, suitable  for  the  different  sizes  of  drill  holes. 
When  engaged  in  rock  excavating,  whether  min- 

125 


Rock    Excavating    and    Blasting 


ing,  quarrying,  tunneling  or  removing  rock  in  con- 
struction work,  the  superintendent  in  charge  will 
do  well  to  secure  from  the  various  manufacturers 
of  explosives  their  catalogues  and  descriptive  mat- 
ter about  the  various  brands  of  explosives  they 
make,  and  the  purposes  for  which  they  are  best 
suited.  Manufacturers  of  explosives,  as  well  as 
independent  experimenters,  are  constantly  at 
work  trying  out  new  formulas,  and  as  soon  as  the 
demand  arises  for  an  explosive  of  any  quality,  the 
demand  is  soon  filled. 


126 


CHAPTER  XII. 


METHODS  OF  THAWING  DYNAMITE. 


HAWING  FROZEN  DYNAMITE. — Froz- 
en dynamite  will  thaw  out  complete- 
ly in  a  very  short  time  if  it  is  sub- 
jected to  a  dry  temperature  of  80 
degrees  Fahrenheit  and  the  cart-, 
ridges  so  arranged  that  the  heat  can  reach  them 
on  all  sides.  Care  should  be  exercised  in  this  pro- 
cess, however,  to  keep  the  temperature  from  ris- 
ing higher  than  necessary,  for  every  degree 
through  which  the  dynamite  is  heated  brings  it 
that  much  nearer  its  firing  point  and  makes  it  so 
much  more  dangerous  to  handle.  It  is  a  danger- 
ous practice  to  thaw  frozen  dynamite  by  passing 
it  through  the  flame  of  a  candle,  heating  it  in  an 
oven  or  holding  it  on  a  shovel  before  the  open 
fire,  for,  while  dynamite  will  frequently  burn  in 
the  open  and  when  unconfined,  it  very  often  ex- 
plodes. 

Convenience,  safety  and  economy  are  all  pro- 
moted by  having  a  suitable  thawing  kettle  or  as 
many  of  them  as  are  needed  on  an  operation,  for 
blasting  cannot  be  properly  conducted  in  cold 

127 


Rock    Excavating    and    Blasting 


weather  without  some  appliance  for  thawing  the 

explosives  and  keeping  them  thawed  until  they 

are  loaded  into  the  bore  holes.    A  thawing  kettle, 

specially  designed  for  thaw- 

ing dynamite  cartridges,  is 

shown  in  Fig.  50.  It  is  sim- 

ply what  is  known  in  the 

kitchen  as  a  double  boiler, 

only    much    larger,    being 

made  in  two  sizes,  having 

capacities    respectively    of 

22  and  60  pounds  of  the  ex- 

plosive.   The  space  between 

the  inner  and  outer  kettles 

is  filled  with  hot  water  or 

with  cold  water  and  placed 

on  a  stove  or  on  a  fire  to        KettleFf0'r 

heat,  and  when  the  water  Dynamite. 

has  been  raised  to  the  right  temperature  the  ket- 

tle is  packed  in  sawdust,  the  dynamite  cartridges 

placed  in  the  inner  compartment  and  a  cloth  of 

some  kind  or  other  non-heat  conducting  material 

placed  over  the  top  to  keep  in  the  heat. 

The  temperature  to  heat  the  water  is  a  question 
which  must  be  considered  when  using  a  thawing 
kettle.  It  must  be  remembered  that  a  tempera- 
ture of  80  degrees  is  all  that  is  required  to  thaw 
dynamite  and  keep  it  in  that  condition,  while  the 
firing  point  is  356  degrees,  or  only  144  degrees 
above  the  temperature  of  boiling  water  in  an  open 
vessel.  It  must  be  still  further  remembered  that 
the  higher  the  temperature  of  the  dynamite  the 

128 


Rock    Ea 


more  unstable  it  is  and  the  more  likely  to  be  de- 
tonated by  a  slight  shock.  It  is  well,  therefore, 
to  aim  not  to  heat  the  cartridges  to  a  higher  tem- 
perature than  100  degrees  Fahrenheit.  If  a  full 
charge  of  22  or  60  pounds  of  dynamite  is  to  be 
placed  in  a  kettle  and  the  dynamite  is  frozen,  the 
water  may  be  raised  to  the  boiling  point,  because 
the  heat  required  to  raise  the  temperature  of  the 
dynamite  will  lower  the  temperature  of  the  water 
until  they  will  both  be  around  100  degrees  Fah- 
renheit. If  only  a  small  amount  of  dynamite  is 
to  be  thawed,  on  the  other  hand,  or  the  dynamite 
to  go  into  the  kettle  is  not  frozen,  merely  chilled, 
or  being  placed  there  to  keep  from  freezing,  then 
the  water  should  be  heated  only  sufficient  to  per-. 
form  the  work  it  has  to  do  without  raising  the 
temperature  of  the  dynamite  to  a  dangerous  de- 
gree. 

Dynamite  should  never  be  thawed  by  exposing 
it  to  steam  or  soaking  it  in  hot  water,  as  it  will 
lose  some  of  its  strength  and  the  nitroglycerine 
removed  becomes  a  source  of  danger.  For  this 
reason  the  water  in  a  thawing  kettle  should  never 
be  reheated  by  placing  it  over  a  fire  or  on  a  stove, 
as  nitroglycerine  from  the  dynamite  in  the  thaw- 
ing compartment  might  have  been  extracted  and 
leaked  through  to  the  water  compartment.  When 
necessary  to  replenish  the  heat  in  a  thawing  kettle, 
add  warm  water  from  another  vessel.  In  the 
absence  of  a  thawing  kettle,  burying  dynamite  in 
a  water-tight  box  in  fresh  manure  which  is  giving 
off  heat  is  a  safe  and  effective  way  to  either  thaw 

129 


Rock    Excavating    and    Blasting 


or  keep  in  a  plastic  state  dynamite  cartridges. 
The  method  requires  considerable  time,  however; 
a  suitable  manure  pile  is  not  always  available  and 
it  would  seem  more  logical  to  get  a  thawing  kettle 
than  a  special  water-tight  box. 

THAWING  BOXES. — Fresh  manure  is  a  thawing 
agent  which  is  inexpensive,  convenient,  safe  and 


.    0 


Fig.  51. 
Thawing  Box  for  Dynamite. 


usually  readily  obtainable  on  all  large  blasting 
operations  where  horses  form  part  of  the  working 
force  or  equipment.  Manure  is  efficient,  however, 
only  when  it  is  fresh  and  will  give  off  heat.  It  is 
useless  to  take  old  manure  in  which  no  heat  is 

130 


Rock    Excavating    an d    Blasting 


being  given  off  by  the  fermentation  taking  place. 
Time  is  another  element  in  the  thawing  of  dyna- 
mite by  means  of  manure,  for  it  must  be  thawed 
in  large  quantities,  and  the  larger  the  quantity  the 
longer  it  will  take.  The  dynamite  cartridges  must 
not  be  allowed  to  come  in  contact  with  the  manure, 
as  the  moisture  would  draw  more  or  less  nitrogen 
from  the  absorbent.  It  must  be  buried  in  the  man- 
ure, therefore,  either  in  closed  cases  or  in  specially 
designed  boxes  or  magazines  having  walls  lined 
with  manure.  A  box  for  thawing  dynamite  is 
shown  in  Fig.  51,  which  will  give  an  idea  of  how 
to  construct  a  thawing  box  for  manure.  If  there 
is  a  big  heap  of  manure  available,  it  may  be  buried 
in  the  manure  heap.  If,  on  the  other  hand,  man- 
ure is  not  so  plentiful,  a  hole  or  pit  can  be  dug 
in  the  ground  a  sufficient  depth  to  permit  a  good, 
deep  lining  of  manure.  The  box  is  then  placed  in 
the  pit  on  top  of  the  manure  lining,  and  the  sides 
banked  up  to  the  level  of  the  ground.  The  dyna- 
mite cartridges  in  the  cases,  the  tops  of  which 
should  be  removed  before  placing  them  in  the 
thawing  box,  may  now  be  placed  in  position,  and 
the  cover  placed,  then  the  whole  heaped  up  with 
manure.  In  the  course  of  time,  a  nice  even  tem- 
perature will  be  generated  inside  of  the  thawing 
box,  and  all  of  the  dynamite  will  be  thoroughly 
thawed. 

It  is  advisable  to  take  the  covers  off  the  cases 
before  placing  them  in  the  thawing  boxes,  so  that 
sticks  or  cartridges  of  dynamite  can  be  taken  out 
by  simply  removing  the  cover  of  the  box,  and 

131 


Rock    Excavating    and    Blasting 


without  jarring  or  otherwise  disturbing  the  dy- 
namite. Removing  the  cover  further  gives  more 
of  a  chance  for  the  heat  to  reach  the  interior  of 
the  case. 

The  thawing  box  shown  in  the  illustration  is 
made  for  just  two  cases  of  dynamite.  They  can 
be  made  any  size  desired,  however,  just  as  well  as 
for  two  cases.  The  walls  of  the  box  are  made  of 
2-inch  planks,  one  side  higher  than  the  other,  to 
give  a  pitch  to  the  cover.  This  pitch,  together 
with  a  layer  of  galvanized  iron,  sheds  all  moist- 
ure from  the  box  and  keeps  the  contents  dry.  A 
double-wall  manure  box  may  be  used  instead  of  a 
single-wall  box  when  desirable,  the  other  box  or 
wall  serving  as  the  pit  shown  in  the  illustration. 

A  thawing  box  22  by  34  inches  will  be  found 
large  enough  to  hold  two  fifty-pound  boxes  of 
dynamite,  and  will  leave  room  all  around  them  for 
the  heat  to  reach  all  sides.  At  the  same  time  the 
extra  room  will  facilitate  handling  boxes  or  cases 
when  placing  them  in  the  thawing  box  or  taking 
them  out. 

Whether  in  storage  or  in  a  thawing  box  or 
house,  dynamite  cartridges  ought  to  be  placed  so 
they  will  lay  on  their  sides,  not  stand  on  their 
ends,  for  if  standing  on  their  ends  the  nitroglycer- 
ine is  liable  to  ooze  from  the  dope  and  collect  in 
the  bottom  of  the  receptacle. 

THAWING  HOUSES  WITH  MANURE-FILLED 
WALLS.  —  In  Fig.  52  is  shown  the  construction  of 
a  dynamite-thawing  house  with  manure-filled 

132 


Rock    Excavating    and    Blasting 


walls.    It  is  8  by  10  feet  outside  dimensions,  and 
is  7  feet  6  inches  high  inside. 

The  house  has  walls  18  inches  thick,  filled  with 
fresh  manure,  and  possesses  a  storage  capacity 


Fig.  52. 
Thawing  House  for  Dynamite. 


of  from  800  to  1,200  pounds  of  dynamite,  taken 
out  of  the  cases  and  placed  in  a  single  layer  on 
the  slatted  shelves.  This  thawing  house  depends 
for  its  heat  entirely  upon  the  stable  manure  which 

133 


Rock    Excavating    and    Blasting 


fills  the  walls.  The  length  of  time  required  to 
thaw  the  stored  dynamite,  and  the  thickness  of 
the  walls,  are  variable  quantities  and  depend  to  a 
great  extent  upon  the  severity  of  the  climate  and 
the  age  of  the  manure. 

With  good,  active  manure  giving  off  a  large 
quantity  of  heat,  eighteen  inches  of  manure  will 
be  found  sufficient  for  any  ordinary  locality.  A 
thawing  house  of  this  size  and  character  is  adapt- 
ed to  work  requiring  a  large  quantity  of  explosive, 
but  running  through  a  period  of  one  winter  only, 
or  a  few  months  of  cold  weather.  However,  by 
removing  some  of  the  top  boards  from  the  walls 
and  replacing  the  old  manure  with  a  lot  of  fresh 
manure  each  winter,  such  a  thawing  house  can  be 
used  indefinitely. 

The  class  of  materials  used  in  construction  can 
be  changed  to  suit  any  local  conditions.  For  in- 
stance, the  illustration  shows  the  roof  covered 
with  galvanized  sheet  iron.  It  may  be  more  con- 
venient in  some  cases,  however,  to  cover  the  roof 
with  tar  paper  or  some  other  prepared  roofing 
material,  while  in  some  places  the  climatic  con- 
ditions or  the  short  time  for  which  the  house  is  to 
be  used  will  permit  the  omission  of  any  other 
covering  than  the  sheathing. 

On  the  other  hand,  in  some  places  it  may  be  ad- 
visable to  cover  the  walls  as  well  as  the  roof  with 
sheet  metal  or  other  like  material. 

This  thawing  house  possesses  one  bad  feature. 
It  is  so  arranged  that  it  is  necessary  to  enter  to 
get  dynamite  or  place  it  on  the  shelves. 

134 


Rock    Excavating    and    Blasting 


As  the  house  is  both  warm  and  convenient, 
there  will,  therefore,  be  a  probability  of  using  it 
as  a  place  in  which  to  make  up  the  primers  for  the 
blasts,  unless  regulations  to  the  contrary  are  em- 
phatically enforced. 

STEAM  THAWING  HOUSE. — Permanent  houses 
for  thawing  dynamite  are  preferably  heated  with 
exhaust  steam  or  hot  water.  So  far  as  the  method 
of  construction  is  concerned,  there  is  no  difference 
between  the  construction  of  a  steam-heated  thaw- 
ing house  and  one  heated  with  hot  water,  except 
that  when  exhaust  steam  is  used  the  supply  is  ob- 
tained from  the  engine,  or  pump  house,  while, 
when  the  thawing  house  is  to  be  heated  with  hot 
water,  a  special  heater  house  will  be  required, 
unless  the  boiler  house  already  on  the  premises 
happens  to  be  so  located  that  it  can  be  used. 

Exhaust  steam  is  usually  the  most  convenient 
and  inexpensive  heat  that  can  be  used,  for  at  the 
majority  of  permanent  works  where  explosives 
are  used  there  is  an  engine  or  pump,  the  exhaust 
steam  from  which  can  be  used  at  practically  no 
cost  for  the  heat  required  in  the  coils  of  the 
thawing  house. 

Live  steam  is  dangerous  to  use,  because  of  the 
high  temperatures  of  steam  under  pressure. 
Eighty  pounds  is  a  comparatively  low  pressure  for 
steam  driving  an  engine  or  pump,  but  at  that  com- 
paratively low  pressure  steam  has  a  temperature 
of  about  324  degrees  Fahrenheit,  while  the  dyna- 
mite has  a  firing  point  of  only  356  degrees  Fah- 

135 


Rock    Excavating    and    Blasting 


renheit.  At  a  pressure  of  only  131  pounds  per 
square  inch,  a  pressure  commonly  carried  in  power 
plants,  the  temperature  of  the  steam  is  356  de- 
grees Fahrenheit,  the  firing  point  of  dynamite.  It 
will  be  seen,  therefore,  how  necessary  it  is  not  to 
have  live  steam  for  thawing  purposes,  for  if  some 
of  the  workmen  were  to  carelessly,  ignorantly  or 
recklessly  attempt  to  thaw  out  sticks  of  dynamite 
on  the  steam  coils,  as  they  sometimes  do,  there 
would  in  all  probability  be  an  explosion  if  steam 
of  sufficient  high  pressure  were  being  used. 

It  is  well  to  keep  a  thermometer  on  the  back 
wall  of  the  thawing  house,  in  what  ought  to  be  the 
hottest  part  of  the  interior,  and  have  a  double 
glass  window  in  front  of  this  thermometer,  so 
the  temperature  of  the  interior  can  be  determined 
without  opening  the  door  and  admitting  cold  air. 
A  damper  should  also  be  placed  in  the  ventilation 
flue  to  permit  the  regulation  of  the  air  circulating 
through  the  house. 

A  thawing  house  suitable  for  the  use  of  either 
exhaust  steam  or  hot  water  is  shown  in  Fig.  53. 
In  this  case,  however,  a  heater  house  is  incorpor- 
ated, showing  the  method  of  connecting  up  the 
water  heater  with  the  heater  coils. 

It  will  be  noticed  that  the  house  cannot  be  en- 
tered. On  the  contrary,  the  dynamite  is  placed  on 
and  taken  from  wooden  trays  or  drawers  which 
slide  in  and  fill  the  compartments  where  they  are 
located.  It  follows  that  it  is  impossible  to  use 
such  a  house  as  a  place  for  priming  cartridges  or 
doing  other  work  of  a  like  dangerous  character. 

136 


?\      Rock    Excavating   and    Blasting 


137 


Rock    Excavating    and    Blasting 


It  ought  to  be  needless  to  add  that  the  thawing 
house  should  always  be  kept  locked  and  that  only 
one  person  should  have  possession  or  custody  of 
the  key  to  the  lock. 

The  heating  coils  for  a  thawing  house  must 
never  be  placed  in  that  portion  of  the  building 
where  the  trays  are  located,  but  must  be  installed 
in  a  little  lean-to  attached  to  the  thawing  house, 
and  from  where  the  heat  from  the  coils  can  spread 
to  the  tray  racks.  It  is  well  to  so  construct  the 
lean-to  that  air  will  circulate  freely  through,  in  at 
the  bottom  from  the  dynamite  trays,  up  through 
the  heater  coils,  and  out  again  at  the  top  into  the 
thawing  room.  The  amount  of  heating  surface 
required  in  the  steam  or  hot  water  coils  will  have 
to  be  worked  out  in  each  case.  It  will  depend 
upon  the  size  of  the  building,  the  way  it  is  built, 
and  the  climate  where  the  thawing  house  is  to  be 
located.  In  severe  climates,  also  where  there  is 
a  variable  climate,  it  will  be  well  to  have  the  coils 
in  sections  and  controlled  from  the  outside,  so 
that  sections  can  be  thrown  into  service,  or  cut 
out  as  occasion  requires.  The  aim  is  to  keep  the 
interior  of  the  thawing  house  and  its  contents  at 
a  uniform  temperature  of  about  80  degrees  Fah- 
renheit. 

The  walls  of  the  house  must  be  carefully  looked 
after,  as  they  must  be  well  insulated.  Either  sand 
or  sawdust  may  be  used  for  this  purpose  when  the 
thawing  house  is  in  a  protected  place,  out  of  dan- 
ger of  rifle  shot.  When  there  is  a  possibility  of 
the  building  being  used  as  a  target  for  rifle  prac- 

138 


Rock    Excavating    and    Blasting 


tise  by  careless  persons,  however,  it  is  better  to 
use  sand  for  the  filling  material,  the  same  as  in 
magazines  for  the  storage  of  dynamite.  The  pre- 
caution to  use  coarse,  dry  sand,  but  not  coarse 
gravel,  should  be  observed  here  the  same  as  in  the 
case  of  storage  magazines,  and  for  the  same  rea- 
son. 

The  size  of  house  to  build  will  depend  upon  the 
quantity  of  dynamite  that  is  to  be  thawed.  The 
size  is  regulated  to  a  great  extent  by  the  size  of 
trays.  The  trays  are  made  18  by  30  inches  inside 
measurement,  by  5  inches  deep,  and  are  designed 
to  hold  50  pounds  of  dynamite  each.  Ten  inches 
space  in  height  is  allowed  for  each  of  the  trays, 
and  a  tier  of  five  trays  allowed  to  each  compart- 
ment. Two  such  tiers  would  make  a  thawing 
house  holding  500  pounds  of  dynamite,  and  if  a 
larger  building  is  required,  it  can  be  increased  in 
units  of  250  pounds  each,  making  at  the  same 
time  a  corresponding  increase  in  the  size  of  the 
steam  or  hot  water  coils. 

A  dynamite  tray  for  a  thawing  house  is  shown 
in  Fig.  54.  The  bottom  of  the  tray  is  either  slat- 
ted or  perforated,  to  allow  the  circulation  of  air. 
When  hot  water  is  the  heating  medium  used,  the 
heater  house  must  be  situated  at  a  sufficiently  low 
level,  so  that  there  will  be  a  rise  of  at  least  1 
inch  in  10  feet  in  the  pipe  from  the  top  of  the 
heater  to  the  hot  water  coils  in  the  leant-to  of  the 
thawing  house.  If  this  grade  is  lacking  there  will 
be  no  circulation  of  hot  water,  but  steam  will 
form  in  the  heater  and  make  a  rattling,  snapping 

139 


^V*\      Rock    Excavating    and    Blasting 

sound.  For  safety  sake  the  system  must  never 
be  a  closed  one,  but  must  be  open  and  provided 
with  an  expansion  tank  to  prevent  the  pressure 
ever  rising  above  that  due  to  the  head  of  water. 
If  the  water  were  confined  in  a  closed  circuit,  pres- 
sure would  be  generated,  and  as  the  temperature 
of  boiling  water  and  steam  are  the  same  under 


»  V, 

^ 

I*T 

! 

| 

WW  »3 

k\H    fcM   ttU   kM   M   HI   NX 

i  Ma  M  r\-  ra 

Dyr?&/7?/'fe  Tray. 

Fig.  54. 

equal  pressures,  the  water  in  a  closed  hot-water 
system  could  be  made  as  hot  and,  therefore,  as 
dangerous  as  steam  in  a  direct  steam  system  us- 
ing high  pressure.  There  would  likewise  be  the 
additional  danger  of  a  boiler  explosion,  with  the 
possible  detonation  of  the  dynamite.  With  an 

140 


Rock    Excavating    and    Blasting 


open  system  of  hot  water  heating,  on  the  other 
hand,  the  temperature  of  the  water  can  never  rise 
above  212  degrees  in  the  heater,  and  would  be 
much  less  than  that  at  the  coils,  so  that  the  dan- 
ger of  overheating  is  thus  minimized  by  using  an 
atmospheric  system  of  hot  water  heating. 

Distance  of  the  heater  house  from  the  thawing 
house  is  another  condition  that  requires  consid- 
eration. A  distance  of  from  30  to  50  feet  has 
been  found  the  most  satisfactory.  Too  close  prox- 
imity of  the  heater  house  to  the  thawing  house, 
that  is,  a  distance  of  less  than  30  feet,  adds  to  the 
fire  risk,  while  too  great  a  distance,  that  is,  fur- 
ther than  50  feet,  increases  the  cost  of  construc- 
tion and  diminishes  the  economy  of  operation; 
The  aim  should  be,  then,  to  strike  the  happy  med- 
ium between  the  two  extremes. 

The  exposed  piping,  of  course,  must  be  well 
insulated,  or  a  frozen  pipe  and  interrupted  ser- 
vice will  result.  The  best  of  pipe  covering  is  none 
too  good  for  this  purpose,  and  non-combustible 
covering  material  would  be  preferable  to  combus- 
tible materials. 

At  permanent  works,  an  inexpensive  way  to 
keep  dynamite  from  freezing  is  to  store  it  in  a 
stone,  concrete  or  brick  vault  below  the  surface  of 
the  ground,  and  well  below  the  frost  line.  The 
roof  can  be  tightly  roofed  over  and  banked  with 
earth  or  manure. 

Perhaps  no  better  advice  could  be  given  in  this 
chapter  on  dynamite  than  to  incorporate  the  rules 
to  be  observed  in  handling  dynamite,  sent  out  with 

141 


Rock    Excavating    and    Blasting 


each  shipment  of  high  explosives  by  the  DuPont 
Powder  Company: 

Never  under  any  circumstances  forget  that  it  is 
an  explosive,  and  must  be  treated  as  such. 

Do  not  store  blasting  caps  or  electric  fuses  near 
dynamite.  They  are  easily  exploded,  but  by  them- 
selves do  only  local  damage.  If  they  are  in  the 
vicinity  of  dynamite  they  might  set  it  off  and 
cause  great  loss. 

Do  not  carry  or  transport  blasting  caps  or  elec- 
tric fuses  together  with  dynamite. 

Never  expose  dynamite  to  the  direct  rays  of  the 
sun,  a  fire  or  hot  stove.  Never  roast,  toast  or 
bake  it  in  any  way. 

Never  put  it  on  or  in  a  stove  or  oven,  on  hot 
steam  pipes  or  on  any  hot  metal. 

Never  fire  into  dynamite  with  a  rifle  or  pistol, 
either  in  or  out  of  a  magazine. 

When  a  shot  misses,  never  dig  it  out.  Take 
plenty  of  time  before  investigating. 

Never  use  a  metal  tamping  rod.  Wood  is  the 
only  safe  material. 

Never  attempt  to  use  frozen  dynamite.  Thaw 
it  first. 

Never  store  dynamite  in  a  wet  or  damp  place. 

Never  leave  it  in  a  field  where  stock  can  get  at 
it.  Cattle  like  the  taste  of  dynamite,  but  it  would 
probably  make  them  sick. 

All  explosive  material  should  be  kept  in  a  suit- 
able dry  place,  under  lock  and  key,  and  where  chil- 
dren or  irresponsible  persons  cannot  get  at  it. 

142 


Rock    Excavating    and    Blasting 


GUNCOTTON  AND  BLASTING  GELATINE. 

GUNCOTTON. — Guncotton  is  a  highly  explosive 
compound  prepared  by  treating  cotton  or  other 
cellulose  materials  with  strong  nitric  and  sul- 
phuric acids.  Ordinary  cotton  of  commerce  is  the 
cellulose  material  most  commonly  used  for  this 
purpose. 

Guncotton  is  highly  inflammable,  burning  with- 
out ash,  but  quietly  unless  under  compression, 
when  it  will  explode.  It  is  largely  used  as  an  in- 
gredient in  smokeless  powder,  but  as  an  explosive 
it  has  been  largely  superseded  by  dynamite. 
When  dry,  guncotton  is  very  sensitive  and  easily 
exploded,  but  when  wet  with  from  15  to  30  per 
cent,  of  water  it  is  insensitive  to  all  ordinary 
shocks.  While  in  this  condition,  however,  it  may 
be  caused  to  detonate  by  detonating  dry  guncotton 
in  contact  with  it.  The  dry  guncotton  can  be  de- 
tonated in  a  number  of  ways,  but  the  surest  and 
most  convenient  is  by  means  of  a  fuse  of  fulmi- 
nate of  mercury  or  a  detonator  of  the  same  ma- 
terial in  a  rubber  sack  in  contact  with  the  dry 
guncotton. 

Guncotton  differs  but  little  in  appearance  from 
ordinary  cotton,  but  it  is  harsher  to  the  touch  and 
less  flexible.  It  is  insoluble  in  hot  or  cold  water, 
but  it  is  readily  soluble  in  many  other  liquids,  not- 
ably a  mixture  of  ether  and  alcohol.  Guncotton 
by  itself  is  not  much  used  for  rock  blasting,  but 
it  forms  the  base  of  a  number  of  powerful  pow- 
ders, among  which  are  "Tonite,"  consisting  of 

143 


Rock    Excavating    and    Blasting 

guncotton  52.5  per  cent,  and  barium  nitrate  47.5 ; 
and  "Potentite,"  consisting  of  66.2  per  cent,  of 
guncotton  and  33.8  per  cent,  of  potassium  nitrate. 
Blasting  gelatines  are  also  made  from  guncotton 
mixed  with  some  solvent. 

The  explosive  force  of  guncotton  has  been  found 
to  be  more  than  fifty  times  that  of  equal  weights 
of  gunpowder. 

BLASTING  GELATINE. — Blasting  gelatine  is  a 
compound  of  guncotton  and  nitroglycerine  in 
which,  strange  to  say,  the  qualities  of  both  explo- 
sives are  so  far  modified  that  the  resulting  blast- 
ing gelatine,  while  retaining  nearly  all  of  the  ex- 
plosive force  of  its  true  constituents,  is  made  less 
sensitive  than  either.  It  is  probably  the  safest 
of  the  high  explosives,  wTith  the  exception  of  wet 
guncotton.  Blasting  gelatine  is  a  yellowish  brown, 
jellylike  mass,  having  a  specific  gravity  of  1.6. 
It  does  not  absorb  water,  nor  is  it  affected  by 
water,  being  only  slightly  affected  at  the  surface 
when  immersed  in  water.  This  property  makes 
it  more  suitable  than  dynamite  for  use  in  wet 
places,  for  under  the  action  of  water  the  nitro- 
glycerine in  dynamite  has  a  tendency  to  exude. 

When  unconfined,  blasting  gelatine  burns  with 
a  hissing  sound,  but  will  not  explode.  When  con- 
fined it  explodes  at  a  tempreature  of  399  degrees 
Fahrenheit,  which  is  43  degrees  above  the  firing 
point  of  either  nitroglycerine  or  dynamite.  It 
freezes  at  a  temperature  of  35  to  40  degrees  Fah- 
renheit, and  when  frozen  is  far  more  sensitive 

144 


Rock    Excavating    and    Blasting 


than  when  unfrozen,  which  makes  it  unsuitable 
for  extremely  cold  climates  but  rather  suitable 
for  warm  ones. 

Closely  allied  to  blasting  gelatine  are  gelatine 
dynamites,  which  are  formed  by  absorbing  blast- 
ing gelatine  in  an  active  base  in  a  similar  manner 
to  making  ordinary  dynamite  by  absorbing  nitro- 
glycerine with  a  dope.  Many  of  the  dynamites  of 
commerce  are  really  gelatine  dynamites,  they  gen- 
erally being  packed,  shipped,  classed  and  other- 
wise treated  as  dynamites.  Different  grades  of 
gelatine  dynamites  are  made  with  a  view  of  pro- 
viding a  suitable  explosive  for  every  known  con- 
dition. Among  the  advantages  claimed  for  this 
kind  of  high  explosives  are  that  the  gases  pro- 
duced are  less  injurious,  therefore  in  tunnel  driv- 
ing the  drill  runners  and  muckers  can  return  to 
their  work  with  less  loss  of  time  and  be  in  better 
physical  condition  during  the  rest  of  their  shift. 
Gelatine  dynamite  is  heavier,  bulk  for  bulk,  than 
ordinary  dynamite  and  consequently  can  be  more 
easily  loaded  in  water.  Being  heavier  allows  a 
shorter  charge  to  be  used,  thereby  saving  the  ex- 
tra depth  of  drill  hole.  It  is  less  affected  by  water, 
which  makes  it  more  suitable  for  submarine  work 
and  wet  work,  and  being  plastic  it  will  stick  in 
upward  drilled  holes  and  not  be  jarred  out  by 
other  shots. 

Among  the  gelatine  dynamite  group  are  the  fol- 
lowing well-known  commercial  brands:  Hercules 
gelatine,  Atlas  gelatine,  Repawno  gelatine,  Giant 
gelatine,  ^Etna  gelatine  and  Forate.  All  the  ex- 

145 


Rock    Excavating    and    Blasting 


plosives  of  the  dynamite  group,  that  is  the  high 
explosives  such  as  guncotton,  blasting  gelatine  and 
gelatine  dynamites,  are  handled  and  stored  like 
dynamite,  and  are  generally  classed  as  such.  Gun- 
cotton  should  be  excepted  from  this  list  to  a  cer- 
tain extent,  for  instead  of  keeping  guncotton  dry, 
it  is  kept  wet,  as  it  is  less  liable  to  detonation  while 
in  that  condition.  It  is  well  for  the  quarryman 
and  miner  to  know  the  differences  between  the 
various  explosives,  their  peculiarities  and  proper- 
ties, as  this  knowledge  makes  more  safe,  or  less 
dangerous,  the  handling  of  them. 


146 


CHAPTER  XIII. 


DETONATORS  FOR  EXPLODING  CHARGES. 


ULMINATE  OF  MERCURY.—  Fulmin- 
ate of  mercury,  one  of  the  most 
sensitive  and  violent  explosives 
known,  and  therefore  one  of  the 
most  dangerous,  is  not  used  as  a 
blasting  agent  but  merely  as  a  detonator  for  ex- 
ploding charges  of  other  explosives.  Fulminate 
of  mercury  is  in  fact  never  handled  except  in  very 
small  quantities.  It  is,  however,  almost  indis- 
pensable in  work  with  other  explosives,  because 
the  shock  resulting  from  its  detonation  has  some 
peculiar  characteristics,  not  fully  understood,  by 
reason  of  which  it  can  detonate  any  high  explo- 
sive with  which  it  is  in  contact.  Moreover,  the 
flame  from  its  detonation  ignites  and  so  explodes 
blasting  powder.  Fulminate  of  mercury  explodes 
when  heated  to  305  degrees  Fahrenheit. 


DETONATORS  OR  BLASTING  CAPS. — The  most 
common  example  of  the  use  of  fulminate  of  mer- 
cury is  in  the  percussion  caps  for  ordinary  shot- 
gun shells,  cartridges  for  rifles  or  revolvers,  and 

147 


Rock    Excavating    and    Blasting 


such  purposes.  In  rock  blasting  the  blasting  cap 
shown  in  Fig.  55  is  likewise  charged  with  this  sen- 
sitive explosive,  which  is  used  in  connection  with 
safety  fuse  to  detonate  high  explosives.  These 


Fig.  55. 
Blasting  Cap. 


caps  are  readily  affected  by  moisture,  and  must  be 
kept  perfectly  dry  until  used.  They  are  put  up 
in  lots  of  100  in  tin  boxes,  and  these  tin  boxes  are 
packed  in  wooden  cases  containing  respectively 
500,  1,000,  2,000,  3,000  and  5,000  blasting  caps. 
In  Table  XII  can  be  found  the  trade  name,  mark- 
ing and  sizes  of  DuPont  blasting  caps. 


TABLE    XII. 

Sizes  of  Blasting  Caps. 


Name  and 
Number  of 
Caps 

Silver 
Medal 
No.  3 

Gold 
Medal 
No.  4 

Du 

Pont 
No.  5 

Du 
Pont 
No.  6 

Du 
Pont 
No.  7 

Du 
Pont 

No.  8 

Color  of 
Box 

Silver 

Gold 

Blue 

Red 

Brown 

Green 

Length  of 
Caps 

1" 

1" 

1J4" 

IK" 

i*A" 

IV 

Blasting  caps  must  be  kept  perfectly  dry,  and 
it  is  well  not  to  take  the  detonators  into  a  wet  or 
damp  working  until  they  are  actually  needed,  as 
they  deteriorate  rapidly  underground  or  in  a  damp 

148 


Rock    Excavating    and    Blasting 


place.  For  example,  according  to  some  experi- 
ments made  in  Leadville  a  number  of  years  ago, 
fresh  caps  which  gave  complete  detonation,  when 
kept  underground  for  twenty-four  hours  gave  in- 
complete detonation;  after  forty-eight  hours  un- 
derground, they  gave  incomplete  detonation  with- 
out red  fumes.  After  seventy-two  hours  under- 
ground, one  of  the  caps  exploded  without  detona- 
tion, and  finally,  after  being  underground  one 
hundred  and  forty-four  hours,  or  six  days,  prac- 
tically a  work  week,  the  caps  refused  to  explode. 

The  strength  of  the  blasting  caps  should  like- 
wise be  considered,  for  it  is  poor  economy  besides- 
increasing  the  danger  to  use  weak  detonators.  A 
strong  blasting  cap  will  not  only  bring  down  from 
10  per  cent,  to  25  per  cent,  more  material  when 
used  to  detonate  a  charge  of  explosive  than  where 
weakened  caps  are  used,  but  there  is  less  danger 
of  a  strong  cap  missing  fire  and  a  missed  shot  is 
not  only  a  financial  loss  but  a  source  of  danger. 
In  the  table  of  sizes  of  blasting  caps  the  numbers 
3,  4,  5,  6,  7  and  8  refer  to  the  strength  of  the  caps 
—  the  higher  the  number,  the  higher  the  strength. 
As  different  manufacturers  use  different  amounts 
of  fulminate  of  mercury  in  the  caps,  only  the  ap- 
proximate strengths  can  be  given.  What  are 
known  as  single-strength  and  double-strength  caps 
are  not  used  in  the  United  States.  Triple-strength 
caps,  the  weakest  used  here,  contain  from  41/2  to  5 
grains  of  fulminate  of  mercury.  Quadruple 
strength  contains  from  6  to  7  grains;  quintuple 
strength,  8  to  9  grains;  the  next  size,  10  to  11 

149 


Rock    Excavating    and    Blasting 


grains ;  then  come  12  to  15  grains,  19,  23  and  31 
grains  respectively. 


MEANS  OF  FIRING  EXPLOSIVES. 

FIRING  WITH  FUSES. — Blasting  powders  may  be 
fired  by  means  of  squibs,  fuses  or  safety  fuses 
with  blasting  caps,  for  blasting  power  explodes 
upon  being  ignited,  and  any  safe  means  that  will 
cause  ignition  may  be  used.  High  explosives,  on 
the  other  hand,  must  be  detonated,  and  for  this 
purpose  a  safety  fuse  with  blasting  cap  or  an  elec- 
tric fuse  or  detonator  must  be  used.  Fuses  defer 
the  time  of  explosion  to  allow  the  quarryman  to 
reach  a  place  of  safety  before  the  blast  takes  place. 
Once  the  fuse  has  been  lighted,  however,  he  has 
no  further  control  over  the  time  of  explosion  than 
that  provided  for  in  the  length  and  make  of  fuse 
used.  With  electric  firing,  on  the  contrary,  every- 
thing can  be  put  in  readiness  and  the  time  of  fir- 
ing deferred  to  suit  the  operator's  convenience,  a 
simple  pulling  up  or  pushing  down  of  the  handle 
of  the  blasting  machine  causing  the  explosion.  It 
will  be  seen  that  in  electric  blasting,  therefore, 
the  time  of  the  blast  is  completely  under  the  oper- 
ator's control,  which  makes  this  the  safest  means 
of  firing  explosives. 

DESCRIPTION  OF  A  FUSE. — A  fuse  is  a  tube, 
generally  flexible,  filled  with  an  inflammable  com- 
pound, or,  what  is  more  commonly  the  case  in 
blasting,  a  cord  or  tape  inflammable  itself,  or  im- 

150 


Rock    Excavating    and    Blasting 

pregnated  with  an  inflammable  substance,  usually 
slow  burning  and  intended  to  convey  fire  to  an  ex- 
plosive or  combustible  mass,  but  so  slowly  as  to 
allow  the  escape  of  the  person  lighting  it.  While 
fuses  are  generally  made  slow  burning  for  rock 
blasting,  there  are  also  made  quick-acting  fuses, 
some  of  them  almost  instantaneous  in  their  action. 
It  is  well,  therefore,  to  test  a  fuse  before  using  it 
by  noting  the  rate  of  burning  of  a  short  piece. 
The  rate  of  burning  of  ordinary  fuses  varies  from 
18  inches  to  4  feet  per  minute.  For  most  pur- 
poses a  fuse  with  a  rate  of  2 
feet  per  minute  will  be  found 
the  most  satisfactory. 

Fuses  are  shipped  in  coils 
as  shown  in  Fig.  56.    They  are 
rig.  se.  put  up  in  cases  of  500  feet, 

1,000  feet,  2,000  feet,  3,000 
feet,  4,000  feet,  5,000  feet,  6,000  feet,  and  in  bar- 
rels of  8,000  feet.  It  might  seem  needless  to  say 
that  fuses  should  be  stored  in  a  cool,  dry  place, 
and  out  of  contact  with  oil.  The  interior  of  the 
place  of  storage  should  further  be  kept  free  from 
sudden  changes  of  temperature.  Fuses  are  made 
in  a  number  of  grades,  depending  upon  the  char- 
acter of  work  for  which  they  will  be  used.  In 
Table  XIII  will  be  found  the  several  grades  put 
out  by  the  DuPont  Company  and  the  uses  for 
which  they  are  intended. 

While  certain  grades  of  fuses  can  be  depended 
upon  for  very  wet  work,  or  even  work  under 
water,  they  cannot  be  relied  upon  to  give  satis- 

151 


g}      Rock    Excavating    and    B lasting 


factory  results  in  submarine  work  or  under  any 
depth  of  water.  Blasting  in  this  kind  of  work 
should  always  be  done  by  electricity,  as  in  sub- 
marine work  the  pressure  might  force  water  into 
the  cartridge  or  fuse,  saturating  them  and  render- 
ing them  useless. 

TABLE   XIII. 
Name  and  Use  of  Fuses. 


Dry  Work  or  Damp 
Work 

Wet  Work 

Very  Wet  Work  or 
Work  Under  Water 

Single  Tape 

Double  Tape 
Crescent 
Reliable 

Triple  Tape 
Stag 

FIRING  WITH  FUSE  AND  CAP. — As  was  previ- 
ously pointed  out,  blasting  powder  can  be  fired 
by  means  of  a  fuse  without  the  aid  of  a  cap,  but 
for  dynamite  or  other  high  explosive  some  form  of 


Fig.  57. 
Fuse  Attached  to  Blasting  Cap. 

detonator  must  be  used,  which  in  turn  may  be 
fired  by  a  fuse.  To  prepare  the  cap  and  fuse  for 
use,  the  fuse  is  cut  off  square  across,  never  at  an 
angle,  so  fire  cannot  sputter  out  the  side  and  ig- 
nite the  explosive  before  the  cap  has  a  chance  to 
detonate,  and  so  the  cap  can  be  given  a  good  hold 

152 


Rock    Excavating    and    Blasting 


when  crimped  onto  the  fuse.  The  cap  is  next 
crimped  onto  the  fuse  as  shown  in  Fig.  57,  by 
means  of  a  pair  of  special  crimping  pliers  or  cap 
crimpers.  This  crimping  should  never  be  done 
by  means  of  the  teeth  or  by  pounding  the  cap  with 
an  iron  bar,  and  care  should  be  taken  to  crimp 
the  cap  near  the  open  end  so  that  the  fulminate 
in  the  other  end  of  the  cap  will  not  be  disturbed, 
for  if  the  fulminate  should  happen  to  be  tightly 
pinched  an  explosion  might  result. 

When  the  fuse  is  properly  capped,  next  fold 
back  the  paper  from  one  end  of  the  dynamite 
cartridge  and  with  a  sharp  stick  like 
a  lead  pencil  but  of  just  the  right  size 
for  the  cap  to  slip  into  the  opening 
made,  gently  make  a  hole  in  the  top 
of  the  dynamite  and  in  this  hole  push 
the  blasting  cap,  as  shown  in  Fig.  58, 
then  tie  the  paper  to  the  fuse,  as  shown 
in  the  illustration.  Instead  of  making 
the  hole  parallel  with  the  axis  of  the 
dynamite  catridge  it  can  be  made  slant- 
ing to  one  side,  so  the  fuse  will  be  along 
one  side  of  the  bore  hole  and  out  of  the 
way  of  the  tamping.  Some  rock-men 
extend  the  hole  down  to  the  center  of 
the  cartridge  so  that  the  detonation 
will  take  place  in  the  center  of  the  Bla^jfng58cap 
dynamite.  It  is  a  question,  however,  %a?g}5™elte 
whether  anything  is  gained  by  that  method,  while 
carrying  the  fuse  through  a  couple  of  inches  of 
the  explosive  is  liable  to  ignite  it,  thereby  causing 

153 


\ 


Rock    Excavating    and    Blasting 


deflagration  of  the  cartridge  instead  of 
detonation.  In  short  cartridges  it 
would  seem  that  the  top  method  of 
priming  was  the  best,  the  only  objec- 

,         tion  being  that  the  fuse  is  more  or  less 
in  the  way  and  apt  to  be  bent  or  in- 

•F-use     jured  by  the  tamping. 

In  long  cartridges,  18  inches  and 
'y  thereabouts  in  length,  if  it  is  deemed 
advisable  to  place  the  cap  near  the  cen- 
ter of  the  dynamite,  the  best  way  is  to 
run  the  fuse  down  the  outside  of  the 
cartridge  and  insert  the  cap  through  a 
hole  on  the  side  which  points  down- 
ward, as  shown  in  Fig.  59.  The  fuse 
must  then  be  bound  in  place  with 
strings,  as  shown  in  the  illustration,  to 

Fig.    59. 

Fuse  Attached  prevent  the  cap  being  pulled  out  or 
'cartridge!*    otherwise  displaced  when  placing  the 
cartridge  in  the  bore  hole  and  tamping 
the  drill  hole  for  the  blast. 

All  that  is  then  necessary  is  to  cut  off  the  fuse, 
allowing  a  sufficient  length  of  time  for  the  oper- 
ator to  get  to  a  place  of  safety  before  the  explo- 
sion takes  place.  If  a  two-foot  fuse  is  being 
used,  that  is,  a  fuse  that  burns  two  feet  per 
minute,  and  it  will  take  two  minutes  to  reach  a 
point  or  place  of  safety,  a  fuse  at  least  four  feet 
long  over  all  should  be  used,  while  under  some 
conditions,  such  as  a  difficult  place  to  get  away 
from,  a  greater  length  would  prove  safer.  There 
is  no  advantage  gained  by  placing  the  blasting 

154 


Rock    Excavating    and    Blasting 


cap  at  the  center  of  the  dynamite  cartridge,  be- 
cause the  instant  detonation  takes  place  the  shock 
is  communicated  to  the  entire  mass,  so  that  wher- 
ever the  cap  is  all  parts  of  the  dynamite  are 
equally  affected. 

Some  rock-men  and  miners  when  placing  a 
blasting  cap  in  the  side  of  a  cartridge  make  the 
hole  pointing  upward,  then  bend  the  fuse  back 
again  upon  itself  to  point  toward  the  mouth  of 
the  drill  hole.  Such  a  practice  is  bad  and  should 
be  discouraged,  for  the  sharp  bend  might  pull 
the  fuse  free  from  the  cap,  or  if  it  does  not,  the 
sharp  bend  in  the  fuse  might  be  sufficient  to  cause 
a  break  in  the  train  of  powder  or  choke  the  fuse, 
so  the  fuse  will  snuff  out  and  a  misfire  result. 

LIGHTING  THE  FUSE. — When  all  is  ready  for 
firing  the  shots,  the  quarryman  has  but  little  time 
at  his  disposal  after  he  has  lighted  the  first  fuse, 
and  it  is  important  that  each  fuse  takes  the  flame 
as  he  passes  along.  If  an  ordinary  fuse  be  merely 
cut  off  and  a  match  or  lighter  applied,  the  powder 
will  not  always  ignite  immediately  and  the  lighter 
might  have  to  leave  before  all  the  fuses  are  light- 
ed. In  order  to  make  sure  that  all  the  fuses  take 
fire,  special  flaming  pieces  are  often  provided. 
In  Fig.  60  is  shown  one  method  of  priming  fuses 
for  ignition.  The  end 
of  the  fuse  in  this  case 
is  split  for  a  short  dis- 
tance and  a  wedge  of  G/'anf 

,  Fig.   60. 

giant      pOWder      mtro-         Fuse    Primed    for    Lighting. 

duced    into    the   split.  • 

155 


Rock    Excavating    and    Blasting 


When  giant  powder  is  ignited  in  the  open  it  burns 
with  a  bright,  fierce  flame,  so  that  a  small  piece 
lighted  in  the  end  of  a  fuse  is  almost  sure  to 
ignite  it. 

Another  method  is  shown  in  Fig.  61.    A  piece 
of  candle  wick  dipped  in  kerosense  or  alcohol  is 

twisted  about  the  end 
of  the  fuse,  so  that  all 
that  is  necessary  is  to 
walk  along  the  line  of 
drill  holes  applying 
the  flame  of  a  torch  to 


Lampwick  PrTmtr  for  Fuse.  6ach     Candle     wlck     ln 

turn.      The     kerosene 

soaked  wick  will  immediately  burst  into  flame,  and 
the  flame  from  the  burning  wick  will  ignite  the 
fuse. 

As  it  is  desirable  to  count  the  shots  when  blast- 
ing by  fuse  to  see  that  they  have  all  gone  off,  the 
fuses  ought  to  be  made  of  different  lengths  so 
that  one  shot  will  follow  another  when  they  are 
all  lighted  at  the  same  time.  Having  the  shots 
follow  one  another  instead  of  exploding  simul- 
taneously does  not  give  as  great  disruptive  force, 
but  it  is  safer  for  the  workmen.  Besides,  it  is 
almost  impossible  to  so  time  all  the  fuses  in  a 
battery  that  the  explosions  will  all  take  place 
together.  Electric  blasting  is  the  only  method 
which  will  accomplish  this. 


156 


CHAPTER  XIV 


FIRING  BLASTS  BY  ELECTRICITY. 


DVANTAGES  OF  BLASTING  BY  ELEC- 
TRICITY. —  Blasting  by  electricity  is 
now  conceded  to  be  the  safest,  most 
economical,  most  effective  and  by 
far  the  most  convenient  way  of  fir- 
ing explosives,  surpassing  any  other  for  safety 
and  certainty  of  action.  By  electric  firing  the  en- 
tire strength  of  the  explosive  is  developed  at  the 
same  instant,  less  explosive  being  thus  required 
where  these  are  a  number  of  drill  holes  than 
when  each  hole  is  fired  separately,  as  is  more 
than  likely  to  be  the  case  when  fuses  are  used. 

By  electric  blasting  all  holes  are  exploded  simul- 
taneously, and  if  all  connections  are  properly 
made  there  is  no  possibility  of  a  second  explosion. 
If  a  misfire  occurs  by  reason  of  improper  connec- 
tions, such  missed  hole  will  not  hang  fire  and  ex- 
plode unexpectedly  as  sometimes  occurs  when 
blasting  with  safety  fuses.  Electric  blasting  con- 
sequently eliminates  this  dangerous  feature  in 
connection  with  blasting  operations. 


ELECTRIC  FUSES. — In  electric  blasting  the  elec- 
157 


Rock    Excavating    and    Blasting 


trie  fuse  takes  the  place  of  the  blasting  cap,  and 
is  used  in  connection  with  a  maganeto,  or  "blast- 
ing machine,"  and  copper  wire  instead  of  a  safety 
fuse.  An  electric  fuse  is  shown  in  section  in  Fig. 
62.  The  shell  (a)  is  of  copper  and  has  a  bead  or 


r 


Fig.  62. 
Section  of  Electric  Fuse. 

corrugation  thrown  out  or  pressed  from  the  inside 
to  form  a  locking  device  to  hold  the  sulphur 
cement  (b)  more  firmly  in  place  than  it  would 
be  held  in  a  smooth  cylinder  or  cap.  The  explo- 
sive, which  consists  mainly  of  fulminate  of  mer- 
cury, is  contained  in  the  chamber  (c),  which  is 
sealed  by  the  sulphur  cement  which  likewise  holds 
the  fuse  wires  firmly  in  place. 

The  copper  fuse  wires  (d)  are  covered  with 
insulating  material  sufficient  for  all  ordinary  pur- 
poses, and  the  bare  ends  of  the  copper  wire  pro- 
ject through  at  (e)  into  the  charge  of  fulminate  of 
mercury,  where  they  are  joined  together  by  the 
short  platinum  wire  or  bridge  (f ) .  It  is  the  heat- 
ing of  this  platinum  wire  to  redness  when  an 
electric  current  is  passed  through  it  that  causes 
the  detonation  to  explode  the  dynamite  cartridge. 
Fuses  are  made  with  leading  wires  of  from  four 
to  thirty  feet  in  length.  If  longer  wires  are 
needed  they  may  be  spliced  with  the  usual  twisted 
splice  with  which  all  electric  wires  are  joined, 
then  insulated  with  insulating  tape. 

158 


Rock    Ea 


Electric  fuses  are  made  of  different  strengths, 
and  for  different  purposes,  such  as  for  dry  blast- 
ing and  for  submarine  work.  Illustration  of  an 
electric  fuse  is  shown  in  Fig.  63.  This  fuse  for 


Fig.  63. 
Waterproof  Fuse  for   Submarine   Work. 

submarine  work,  it  will  be  observed,  is  covered 
with  gutta  percha  to  keep  it  from  being  affected 
by  the  water,  and  the  connecting  wires  leading 
down  to  it  must  likewise  be  of  waterproof  quality. 
For  ordinary  work  the  gutta  percha  covering  is 
not  needed  and  is  omitted.  In  rock  excavating  the 
fuses  should  be  ordered  with  wires  long  enough 
to  allow  at  least  eight  inches  to  project  outside  the 
drill  holes  to  be  connected  to  the  connecting  wires. 
The  connecting  wires  should  never  be  of  smaller 
size  than  the  connecting  wires  to  the  electric  fuses. 

PLACING  THE  ELECTRIC  FUSE. — The  electric  fuse 
is  best  placed  in  the  center  of  the  charge,  and  in 
placing  the  electric  fuse  a  hole  is  usually  made  in 
the  side  of  the  cartridge  as  explained  for  a  cap 
and  fuse  in  Fig.  59,  and  the  electric  fuse  inserted 
in  this  cavity,  pointing  downward. 

The  wires  from  the  electric  fuse  are  then  bound 
to  the  cartridge  with  string  to  hold  the  fuse  in 
place,  the  free  ends  being  kept  above  the  mouth 
of  the  drill  hole  for  connecting  to  the  leading 
wires  from  a  magneto.  Instead  of  placing  the 
electric  fuse  in  the  center  of  the  charge,  some 

159 


Rock    Excavating    and    Blasting 


rock-men  place  it  in  the  end  of  the  cartridge  as 
explained  for  blasting  with  fuse,  but  they  then 
turn  the  cartridge  upside  down  and  bind  the  wires 
to  the  cartridge,  as  shown  in  Fig.  64,  so  that  the 
fuse  is  at  the  bottom  of  the  charge  when  loaded 
in  the  bore  hole. 

Care  should  be  taken  when  tamping  a  bore  hole 
that  the  electric  wires  are  not  broken  or  the  in- 
sulating materially  injured,  so  the  cur- 
rent can  short  circuit,  or  there  might  ^ 
be  a  misfire.     In  the  handling  of  the 
electric  fuse  care  is  necessary,  also, 
not  to  break  the  sulphur  cement,  dis- 
arrange the  wires  in  the  fuse,  or  break 
the    fine    platinum    wire    or    bridge. 
Breaking  the  cement  will  leave  a  free 
passage  to  any  water  which  might  be 
in  the  hole,  so  that  the  fuse  will  become 
spoiled  and  a  misfire  result. 

The  platinum  bridge  of  an  electric 
fuse  is  of  necessity  very  small  and 
delicate  in  order  to  keep  down  the  cost, 
and  at  the  same  time  be  capable  of  be- 
ing heated  red  hot  by  the  small  current 
of  electricity  generally  used  for  this 
purpose.  If  this  bridge  or  wire  be  i 
subjected  to  any  great  strain  it  is  liable 
to  become  broken,  thereby  destroying 
the  fuse. 

Sharp  bending  of  the  electric  wires  might  also 
lead  to  a  misfire.  Damaging  the  insulation  so 
the  current  can  short  circuit  will  have  this  effect, 

160 


Dynan 
Carfn 


Rock    Excavating    and    Blasting 


and  the  wires  need  not  touch  to  cause  this  dam- 
age, for  if  they  be  bare  there  might  be  sufficient 
moisture  present  to  rob  that  particular  cap  of 
part  of  its  current,  and  the  result  will  be  the  fuse 
will  miss  fire. 

Two  ELECTRIC  FUSES  IN  ONE  DRILL  HOLE. — 
Two  electric  fuses  are  often  used  in  deep  drill 
holes  where  there  is  a  large  charge  of  explosive, 
so  that  the  cartridge  at  the  two  ends  can  be 
touched  off  simultaneously.  When 
such  is  the  case  the  electric  wires 
to  the  fuses  should  be  connected  in 
series,  as  shown  in  Fig.  65.  One  o'f 
the  wires  from  the  lower  fuse  is 
connected  to  one  of  the  wires  from 
the  upper  fuse,  and  the  two  remain- 
ing free  wires  are  then  brought  to 
the  surface  of  the  ground,  and  the 
entire  charge  then  treated  as  one 
so  far  as  subsequent  wiring  is  con- 
cerned. In  considering  the  capac- 
ity of  a  blasting  machine,  however, 
each  double-fused  drill  hole  or 
charge  must  be  rated  as  two  dis- 
tinct charges,  for  it  takes  just  as 
much  electric  current  to  touch  off 
two  fuses  in  a  single  bore  hole  as  it 
would  to  touch  off  two  fuses  in 
separate  drill  holes. 


Fig.  65 

Two  Electric  Fuses 
in  One  Drill  Hole. 


WIRING  FOR  MULTIPLE  BLASTS. 
— The  manner  of  wiring  for  an 
161 


Rock    Excavating    and    Blasting 


electric  blast  when  a  number  of  charges  are 
to  be  exploded  at  once  is  shown  diagrammatically 
in  Fig.  66.  Starting  at  one  end  of  the  row  of 
drill  holes,  one  pole  of  the  blasting  machine  is 
connected  to  one  fuse  wire  of  the  nearest  hole. 
The  other  fuse  wire  is  connected  by  means  of 
special  connecting  wire  to  one  of  the  fuse  wires 
in  the  next  nearest  hole.  The  free  wire  in  this 
hole  is  in  turn  connected  to  one  of  the  fuse  wires 


Fig.  66. 
Two  Wire  Circuit  for  Multiple  Blasts. 

in  the  next  succeeding  drill  hole,  and  so  on  until 
the  last  hole  is  reached,  when  the  remaining  fuse 
wire  is  connected  by  means  of  a  leading  wire  to 
the  other  pole  of  the  blasting  machine.  It  will  be 
seen  that  by  this  method  of  wiring,  the  electric 
current  must  pass  successively  through  every  fuse 
in  the  lot,  thereby  insuring  them  all  being  deton- 
ated. In  the  illustration  the  blasting  machine  or 

162 


Rock    Excavating    and    Blasting 


magneto  is  shown  in  the  background.  This  is 
merely  to  show  the  entire  apparatus  complete, 
however.  In  practice  the  blasting  machine  would 
be  located  in  some  sheltered  place  out  of  range 
of  the  rock  broken  out  by  the  blast,  and  about  250 
feet  away. 

The  wiring  shown  in  the  illustration  is  for  a 
two-pole  or  two-wire  blasting  machine.     Where 


Fig.  67. 
Three  Wire  Circuit  for  Multiple  Blasting. 

a  great  number  of  blasts  are  to  be  fired  at  the 
same  time,  however,  three-wire  machines  are  fre- 
quently used.  The  manner  of  wiring  for  a  three- 
wire  machine  is  shown  in  Fig.  67.  The  series  of 
drill  holes,  1,  1,  1  form  one  circuit  and  the  series 
2,  2,  2  another  circuit,  which  could  be  fired  separ- 
ately by  bringing  separate  return  leaders  to  the 

163 


Rock    Excavating    and    Blasting 


middle  binding  post  of  the  blasting  machine  or 
may  be  connected  up  in  one  big  circuit,  as  shown 
in  the  illustration,  by  connecting  the  return  wire, 
a,  to  the  connecting  wires  at  the  middle  of  the 
battery  of  drill  holes.  The  wires,  a-b,  form  one 
loop  of  the  circuit,  and  the  wires,  a-c,  the  other 
loop  of  the  circuit,  and  if  only  the  bore  holes  1,  1 
were  to  be  fired  the  wires  would  be  connected  up 
in  the  loop,  a-c,  without  being  joined  to  the  other 
half  of  the  system,  while  if  the  bore  holes  2,  2 
were  to  be  fired  separately  the  wires,  a-b,  would 
be  used,  but  they  would  be  disconnected  from  all 
contact  with  wire  c.  When  a  three-post  blasting 
machine  is  used,  the  size  of  the  leading  wires 
need  not  be  so  large  as  for  two-wire  work,  and 
almost  50  per  cent,  more  fuses  can  be  fired  with 


Fig.  68. 
Joint  for  Electric  Wires. 


the  machine  than  could  be  fired  with  a  two-wire 
blasting  machine  of  equal  size. 

CONNECTIONS  FOR  ELECTRIC  WIRES. — The 
method  of  making  a  straight  splice  or  joint  in 
copper  electric  wires  is  shown  in  Fig.  68.  The 
insulation  is  removed  from  the  ends  of  the  two 

164 


Rock    Excavating    and    Blasting 


pieces  to  be  joined  for  a  distance  of  about  21/2 
inches  back  and  the  wires  scraped  with  a  knife 
to  brighten  them  if  they  have  become  dulled  or 
tarnished.  The  ends  are  next  brought  together 
and  twisted  either  with  fingers  or  pliers  into  the 
connections  shown  in  the  illustration.  When  a 
branch  joint  is  to  be  made,  the  insulation  is  scrap- 
ed off  the  branch  wire  in  the  manner  explained 
and  on  the  main  wire  the  insulation  is  removed 
for  a  distance  of  two  inches  where  the  connection 
is  to  be  made.  The  end  of  the  branch  wire  is  next 
wound  tightly  around  the  main  wire  and  the  con- 
nection is  made.  It  is  very  important  that  the 
wires  when  joined  together  be  perfectly  clean  and 
bright,  and  that  they  be  twisted  together  tight 
and  firm.  If  the  joints  are  not  well  made  or  if 
any  one  of  them  is  defective  it  will  affect  the 
whole  circuit,  perhaps  causing  all  the  holes  to 
misfire. 

The  bare  wire  at  joints  should  never  be  allowed 
to  touch  the  ground,  particularly  if  it  be  wet,  or 
a  ground  current  might  result.  This  can  be 
avoided  by  putting  dry  stones  under  the  wires  at 
the  sides  of  the  joints  to  keep  them  off  the  ground. 
Insulating  tape  may  likewise  be  used  for  this  pur- 
pose, but  in  ordinary  rock  blasting  in  fairly  dry 
places  insulating  the  joint  will  hardly  be  neces- 
sary. 

TWO-POST  BLASTING  MACHINE.  —  Two-post 
dynamo-electric,  or  magneto-electric,  blasting  ma- 
chines of  small  size,  occupying  less  than  one-half 

165 


Rock    Excavating    and    Blasting 


a  cubic  foot  of  space  and  weighing  less  than  twen- 
ty-two pounds,  are  the  kind  most  commonly  used 
for  small  work,  such  as  ordinary  rock  blasting, 
and  on  account  of  their  reliability  they  are  very 
suitable  for  the  purpose. 

The  interior  and  outside  views  of  a  two-post 
blasting  machine  may  be  seen  in  Fig.  69.    In  this 


Fig.  60. 
Two-Post  Blasting  Machines. 

apparatus  there  is  a  magnet,  and  an  armature 
which  by  revolving  between  the  poles  of  the  prin- 
cipal magnet  generates  the  electric  current  which 
explodes  the  charges.  Also  there  is  a  loose  pinion 
which  has  teeth  to  engage  with  the  rack  bar.  By 
clutching  the  spindle  of  the  armature  on  the  down 
stroke  it  generates  the  current  of  electricity,  and 

166 


Rock    Excavating    and    Blasting 


when  it  reaches  the  end  of  its  stroke  breaks  the 
contact  between  the  small  platinum  bearings  at 
the  bottom,  thus  causing  the  whole  charge  or  cur- 
rent of  electricity  to  pass  through  the  firing  circuit 
composed  of  the  leading  wire,  connecting  wire  and 
electric  fuses. 

THREE-POST  BLASTING  MACHINES. — The  inter- 
ior and  exterior  of  a  three-post  blasting  machine, 


Fig.  70. 
Three- Post   Blasting   Machines. 


such  as  is  used  with  three-wire  circuits,  is  shown 
in  Fig.  70.  The  object  attained  by  the  use  of 
the  third  or  middle  post  is  that  when  a  large 
number  of  electric  fuses  are  in  circuit  there  will 
be  less  liability  of  failure  of  some  of  those  near 
the  middle  of  the  circuit,  if  the  big  circuit  is 

167 


@?VO      Rock    Excavating    and    Blasting       C^tf® 

really  broken  up  into  smaller  loop  or  circuits,  and 
a  common  return  brought  back  to  the  blasting 
machine. 

In  firing  in  one  circuit  a  moderate  number  of 
electric  fuses,  only  two  leading  wires  need  be 
used,  but  one  of  these  must  be  connected  with  the 
middle  post  and  the  other  may  be  connected  with 
either  of  the  side  posts. 

The  three-post  machine  requires  more  care  in 
the  handling  and  connecting  up  than  a  two-post 
machine,  and  for  ordinary  blasting  operations  the 
two-post  machine  will  generally  be  found  satis- 
factory. 

THE  CAPACITY  OF  A  BLASTING  MACHINE. — 
Blasting  machines  are  generally  rated  according 
to  the  number  of  fuses  or  "holes"  they  will  fire. 
For  instance,  a  machine  rated  at  from  one  to  ten 
holes  means  that  the  machine  has  sufficient  power 
or  will  generate  sufficient  current  to  detonate  the 
electric  fuses  in  from  one  to  ten  holes  at  once. 
The  difference  between  holes  and  charges  must  be 
clearly  understood,  however.  Sometimes  it  is 
desirable,  as  when  using  deep  holes  with  large 
charges,  to  place  more  than  one  electric  fuse  in 
each  hole.  When  this  is  done  it  must  be  remem- 
bered that  each  fuse  is  to  be  considered  as  a 
charge  or  hole.  It  cannot  be  expected  that  a  ten- 
hole  machine  will  explode  two  or  more  electric 
fuses  in  each  of  the  ten  holes,  for  it  will  not  do 
so.  The  rating  of  the  machines  is  on  the  assump- 
tion that  only  one  fuse  will  be  in  each  hole.  For 

168 


Rock    Excavating    and    Blasting 


each  additional  fuse  put  in  a  bore  hole,  one  hole 
must  be  omitted  or  deducted  from  the  capacity 
of  the  machine. 

"PULL-UP"  AND  "PUSH-DOWN"  BLASTING  MA- 
CHINES.— The  blasting  machines  described  in  this 
chapter  are  what  are  known  as  "push-down"  ma- 
chines. That  is,  the  machines  are  operated  by  a 
downward  stroke  of  the  handle  bar.  The  only  es- 
sential difference  between  this  and  a  "pull-up" 
machine  is  that  in  the  latter  the  upward  stroke  is 
the  effective  motion. 

FIRING  WITH  A  BLASTING  MACHINE. — After  the 
drill  holes  have  been  loaded  all  the  fuse  wires  pro- 
ject from  eight  inches  to  a  couple  of  feet  above 
ground.  These  wires  are  connected  up  in  series, 
as  previously  explained,  the  joints  supported  on 
stones  so  the  bare  wires  will  not  be  in  contact  with 
the  earth,  and  the  free-end  wires  are  then  con- 
nected to  the  blasting  machine.  The  wires  which 
connect  the  fuse  wires  together  are  called  the  con- 
necting wires,  while  the  wires  which  connect  the 
free-end  fuse  wires  to  the  blasting  machine  are 
known  as  the  leading  wires.  The  leading  wires 
are  first  connected  to  the  respective  fuse  wires 
and  the  free  ends  are  carried  back  to  where  the 
blasting  machine  will  be  used,  but  the  ends  of 
the  leading  wires  are  not  attached  to  the  binding 
posts  of  the  machine  until  everything  is  in  readi- 
ness for  blasting.  These  connections  are  then 
.made,  the  operator  lifts  the  handle  of  the  magneto 

169 


^Vf\       Rock    Excavating    and    Blasting        ^^® 

to  its  full  height,  pushes  it  down  slowly  for  the 
first  half  inch  or  so,  and  then  with  all  his  force, 
until  the  rack  attached  to  the  handle  reaches  the 
bottom  of  the  box  and  sends  the  current  through 
the  outer  circuit  to  the  fuses. 

When  operating  the  blasting  machine  the  han- 
dle or  rack  bar  should  never  be  churned  up  and 
down,  but  should  simply  be  given  the  one  vigorous 
downward  push  for  the  "push-down"  machine,  or 
a  similar  upward  pull  for  the  "pull-up"  machine. 

TESTING  A  BLASTING  MACHINE. — A  blasting 
machine  should  always  be  kept  in  good  condition, 
clean,  and  never  abused  or  played  with.  Its 
strength  should  be  tested  from  time  to  time  to 
see  that  sufficient  power  can  be  generated  to  fire 
the  fuses.  A  simple  way  to  test  a  blasting  ma- 
chine is  by  means  of  an  ordinary  incandescent 
electric  lamp.  A  lamp  and  socket  properly  wired 
must  first  be  tested  to  see  that  they  are  in  good 
condition,  the  wires  are  then  attached  to  the  bind- 
ing posts  of  the  machine — to  one  side  post  and 
the  center  post  in  the  case  of  a  three-post  machine 
— as  when  firing  a  blast,  and,  if  the  machine  is 
in  good  condition,  the  lamp  will  show  when  the 
machine  is  operated  a  bright,  incandescent  light 
or  white  flash  if  the  current  be  strong.  If  the 
light  in  the  lamp  cannot  be  made  strong  or  bright 
it  is  evident  that  the  current  generated  is  weak 
and  might  not  fire  a  fuse.  If  the  lamp  does  not 
show  any  light  the  machine  is  out  of  order,  and  a 
blast  cannot  be  fired  with  it  until  repaired.  Most 

170 


Rock    Excavating    and    Blasting 


of  the  misfires  blamed  on  poor  fuses  are  as  a  mat- 
ter of  fact  lack  of  current  from  the  machine. 

Another  way  to  test  a  blasting  machine  is  to 
connect  in  series  above  ground  the  full  number  of 
good  electric  fuses  which  the  machine  should  be 
able  to  explode  if  it  were  in  good  condition.  Next 
connect  these  electric  fuses  in  a  regular  circuit  to 
the  machine,  placing  the  machine  at  a  safe  dis- 
tance so  as  not  to  be  damaged  by  tlie  explosion  of 
the  fuses.  If  the  blasting  machine,  when  properly 
operated,  then  fails  to  explode  all  the  electric 
fuses  in  the  series,  it  is  because  the  current  pro- 
duced by  the  machine  is  weak  and  the  machine 
needs  repairing. 

The  blasting  machine  when  not  in  use  should 
not  be  left  carelessly  lying  around  the  workings, 
but  should  be  kept  in  the  office  or  some  other  dry 
room  until  wanted.  Never  overload  a  blasting 
machine.  It  is  better  to  divide  the  holes  up  into 
two  blasts. 

When  all  the  electric  fuses  connected  to  a  ma- 
chine  do  not  fire,  in  nine  cases  out  of  ten  the  fault 
is  with  the  blasting  machine  or  its  manipulation, 
not  with  the  fuses.  Tests  have  repeatedly  shown 
that  when  some  of  the  holes  in  a  circuit  explode 
and  some  fail  the  cause  is  an  insufficient  amount 
of  electricity.  Generally  this  is  caused  by  the 
blasting  machine  being  in  bad  condition,  or  by  the 
operator  giving  only  a  comparatively  light  push 
to  the  handle. 

SOME  PRECAUTIONS  IN  BLASTING.  —  In  handling 

171 


Rock    Excavating    and 


explosives  and  in  preparing  for  a  blast  too  great 
care  cannot  be  exercised  to  prevent  accidents.  It 
is  a  poor  policy  to  use  a  short  fuse  to  hasten  an 
explosion  or  with  the  idea  that  it  is  economical  to 
do  so,  as  the  blast  might  be  set  off  before  the  oper- 
ator has  time  to  seek  cover.  It  is  likewise  danger- 
ous to  attempt  to  withdraw  a  wire  from  an  electric 
fuse.  An  explosion  of  the  fuse  might  result. 

Never  fire  a  charge  to  chamber  a  hole,  then  im- 
mediately reload  it,  as  the  hole  will  be  hot  and 
might  cause  a  premature  explosion.  When  every- 
thing is  ready  for  the  blast,  do  not  fire  the  shot 
before  everybody  is  well  beyond  the  danger  zone 
and  protected  from  flying  debris.  Protect  th^ 
supply  of  explosives  also  from  danger  from  this 
source. 

In  case  of  a  misfire  or  an  apparent  misfire,  do 
not  be  in  a  hurry  to  seek  an  explanation  of  the 
cause.  Take  plenty  of  time  before  approaching 
the  misfire.  It  might  be  only  a  delayed  explosion. 
In  case  the  charge  has  missed  fire,  don't  bore,  drill 
or  pick  out  the  misfire  shot.  Drill  and  charge 
another  hole  at  least  two  feet  from  the  missed  hole 
and  fire  this  charge. 


172 


CHAPTER  XV. 


HANDLING  AND  STORING  EXPLOSIVES. 


AWS  REGULATING  STORAGE  AND  HAN- 
DLING OF  EXPLOSIVES.  —  In  most 
States  the  handling  and  storage  of 
explosives  is  regulated  by  law,  and 
before  commencing  operations  in 
any  locality  the  one  responsible  for  the  handling 
and  storage  of  the  explosives  should  familiarize 
himself  with  the  requirements  of  the  laws,  and 
then  comply  with  them.  Failure  to  do  so  will  lead 
to  heavy  damages  in  civil  suits,  and  perhaps 
prison  sentence  should  an  accidental  explosion  oc- 
cur and  cause  loss  of  life,  injury,  or  damage. 

The  Interstate  Commerce  Commission  have 
formulated  regulations  for  the  transportation  of 
explosives,  as  have  likewise  the  American  Railway 
Association.  These  instructions  are  contained  in 
a  little  140-page  book  which  can  be  had  for  the 
asking  by  applying  to  any  freight  agent.  It  is  to 
the  interest  of  everybody  handling  and  transport- 
ing or  shipping  explosives,  therefore,  to  secure  a 
copy  and  be  guided  by  the  rules  and  regulations 
there  laid  down. 

173 


Rock    Excavating    and    Blasting 


HANDLING  AND  STORING  OF  BLASTING  POWDER. 
— Blasting  powder  can  be  handled  with  a  high 
degree  of  safety,  still  it  is  advisable  to  remember 
at  all  times  that  it  is  an  explosive,  and  that  reck- 
lessness in  its  handling  should  neither  be  practised 
nor  tolerated.  When  loading  powders  on  cars, 
wagons,  or  other  vehicles  for  transportation  they 
should  be  so  packed  that  they  will  remain  firmly 
in  place  and  not  slide  or  move  about  while  in 
transit.  Kegs  should  likewise  be  protected  from 
snow,  rain,  direct  rays  of  the  sun,  or  extremes 
of  any  kind. 

The  site  for  a  magazine  for  the  storage  of  blast- 
ing powder  should  be  such  that  the  possibility  of 
damage  due  to  an  accidental  explosion  will  be  re- 
duced to  the  minimum.  The  location  should  be  as 
dry  as  possible,  and  should  consequently  never  be 
constructed  against  rock  or  earthen  banks  where 
moisture  could  trickle  in  or  dampness  penetrate. 
The  ground  around  and  beneath  the  magazine 
should  be  well  drained  and  graded,  and  ample 
space  allowed  underneath  the  floor  to  provide  for 
free  circulation  of  air  on  all  sides  of  the  building. 
The  magazine  itself  should  have  provision  made 
for  ventilating  the  interior,  with  means  for  clos- 
ing the  ventilators  during  stormy  weather. 

In  storing  the  powder  the  kegs  should  be  placed 
on  end,  bungs  down,  to  prevent  the  possible  en- 
trance of  moisture  to  the  powder.  The  floor  of 
the  powder  magazine  should  be  kept  scrupulously 
clean,  for  loose  powder  on  the  floor  is  liable  to 

174 


®\§      Rock    Excavating    and    Blasting       CJfl& 

form  a  train  to  carry  flame  from  a  light  to  the 
powder  kegs. 

Fuses  or  caps  should  never  be  stored  in  a  pow- 
der magazine  or  in  a  high-explosive  magazine,  as 
they  are  more  easily  detonated  than  high  explo- 
sives, and  if  detonated  close  to  dynamite  might 
cause  it  to  explode.  If  lightning  rods  are  placed 
on  the  magazine  the  rods  should  have  a  ground 
connection  to  water,  otherwise  they  are  worse 
than  useless. 

No  iron  tools  should  be  used  in  the  magazine, 
and  the  floor  nails  should  be  driven  into  the  floor 
so  their  heads  will  not  project.  In  case  a  keg 
becomes  broken  or  powder  is  spilled  on  the  floor, 
a  wooden  scoop  and  broom  brush  should  be  used 
to  clean  it  up,  never  a  steel  shovel.  It  is  danger- 
ous to  walk  on  loose  powder  in  a  magazine  with 
shoe  nails  projecting  from  the  soles  of  shoes,  as 
they  might  fire  the  powder.  For  this  reason  the 
floor  of  a  powder  magazine  should  be  kept  per- 
fectly free  from  loose  powder. 

MAGAZINES  FOR  THE  STORAGE  OF  DYNAMITE. — 
Permanent  magazines  for  the  storage  of  high  ex- 
plosives are  preferably  made  of  bricks,  stones, 
concrete  or  some  other  equally  fireproof  and  bul- 
letproof materials.  The  magazines  should  be  lo- 
cated in  isolated  spots,  and  surrounded,  if  possi- 
ble, with  high  banks.  Brush,  weeds  and  high 
grass  ought  to  be  kept  trimmed  back  a  sufficient 
distance  to  insure  safety  in  case  of  fire  in  the  un- 
derbrush and  dead  grass  near  by.  As  in  the  case 
of  powder  storage,  the  dynamite  magazine  must 

175 


Rock    Excavating    and    Blasting 


be  well  ventilated  and  at  the  same  time  so  ventil- 
ated that  rain  or  snow  cannot  drift  in  during 
stormy  weather.  The  temperature  m  the  maga- 
zine should  be  regulated  to  about  80  degrees 
Fahrenheit.  The  higher  the  temperature  of  the 


Fig.  71. 
Portable  Dynamite  Magazine. 

explosive  the  more  uncertain  and  unstable  it  be- 
comes, so  that  temperatures  above  100  degrees 
Fahrenheit  become  correspondingly  dangerous. 
Besides,  the  nitrogen,  although  it  has  a  high  boil- 

176 


Rock    Excavating    and    Bias  ting 


ing  point,  evaporates  sensibly  at  a  temperature  a 
little  above  100  degrees,  and  thereby  loses  much 
of  its  strength. 

It  is  not  necessary  to  build  portable  magazines 
or  magazines  for  temporary  use  out  of  bricks, 
stone  or  concrete,  but  they  ought  to  be  made  bul- 
letproof and  fireproof,  or  at  least  fire-retarding, 
if  not  actually  fireproof.  A  portable  or  temporary 
dynamite  magazine  is  shown  in  perspective  in 
Fig.  71.  This  building  is  mounted  on  a  brick 
foundation  and  is  encased  on  the  outside  with 
No.  24  or  No.  26  sheet  metal,  which  may  be  either 
black  or  galvanized.  When  the  cost  of  brick 
foundations  must  be  eliminated,  the  magazine 
may  be  set  on  posts  spaced  from  4  to  6  feet 
centers,  sunk  in  the  ground  below  frost  level,  and 
capped  with  a  6x6  or  larger  sill.  The  outside  of 
the  posts  must  then  be  boarded  like  the  rest  of 
the  building,  clear  to  the  ground,  and  covered  with 
sheet  metal  in  the  same  way,  so  that  fire  cannot 
creep  under  the  building  and  set  fire  to  the  maga- 
zine from  beneath. 

The  details  of  construction  of  a  portable  maga- 
zine can  be  seen  in  Fig.  72.  The  studding  are 
boarded  on  the  outside  with  matched,  or  tongue 
and  groove,  sheathing,  and  the  outer  surface,  both 
sides  and  roof,  covered  with  a  layer  of  No.  24  or 
No.  26  sheet  metal.  This  does  not  make  a  fire- 
proof construction,  but  it  is  fire  retardant,  as  the 
sheet  metal  will  not  burn,  although  it  will  trans- 
mit enough  heat  to  the  wood  within  to  cause  that 
to  take  fire.  The  boards  beneath  the  sheet  metal 

177 


Rock    Excavating    and    Blasting 


will  burn  very  slowly,  however,  owing  to  the  fact 
that  but  little  air  or  oxygen  can  reach  them,  and 
without  air  the  boards  will  char,  forming  char- 
coal. 

To  make  the  walls  bulletproof,  the  inside  of  the 
building  is  lined  with  boards,  the  same  as  the  out- 
side, and  the  space  between  the  inner  and  the 
outer  boards  is  filled  from  sill  to  plate  with  good, 
coarse,  dry  sand.  Instead  of  using  sand  the  maga- 
zine can  be  bulletproofed  by  laying  one  course  of 
bricks  in  cement  mortar  in- 
side the  magazine,  or  filling 
the  spaces  between  the  stud- 
ding with  bricks  laid  in  ce- 
ment mortar.  As  a  rule,  how- 
ever, the  sand  will  be  found 
preferable,  although  coarse 
gravel  is  never  to  be  used,  on 
account  of  the  missiles  that 
would  be  thrown  in  case  of  an 
explosion. 

The  thickness  of  the  walls 
of  sand  required  to  make  a 
^agazine  bulletproof  will  de- 
pend pretty  much  upon  the 
character  of  firearms  used  in 
the  locality.  In  places  where 
smokeless  powder  is  used  in 
high-power  rifles,  such  as  the 
Government  Springfield,  11 
inches  of  sand  are  absolutely 
necessary  to  bulletproof  the 
magazine.  When  the  30-30 
178 


Fig.  72. 

Detail  of  Portable 
Magazine. 


Rock    Excavating    and    Blasting 


Winchester,  or  equivalent,  is  the  strongest  rifle 
in  common  local  use,  8  inches  of  dry  coarse  sand 
filling  is  sufficient.  When  shotguns  and  rifles  not 
heavier  than  32  calibre  are  the  firearms  ordinarily 
used,  6  inches  of  sand  filling  will  bulletproof  the 
magazine.  Nothing  less  than  6  inches  of  sand 
filling,  however,  should  be  used. 


179 


INDEX 


Page. 


Active      Base,      Dynamite 

with  an   121 

Air  Reheaters  84 

Air  Required  for  Drilling 

Machines     61 

Air,    Running    with    Com- 
pressed          45 

Amount  of  Explosive  Re- 
quired       101 

Appearance   of   Dynamite.  122 


Bags,  Tamping 115 

Base,    Dynamite    with    an 
Active     121 

Base,    Dynamite    with    an 

Inactive     120 

Bits  or  Steels,   Rock  Drill    51 

Blacksmith        Tools        for 

Forging  Drill  Steels..     Gl 

Blasting  Caps  147 

Blasting,  Explosives  Used 

in    91 

Blasting,   Free  Faces  in..      4 

Blasting   Machine,    Capac- 
ity of  a 168 

Blasting    Machine,    Firing 
with  a    169 

Blasting  Gelatine   344 

Blasting   Machines,   "Pull- 
Up"  and  "Push-Down"  169 

Blasting     Machine,     Test- 
ing  a    170 

Blasting    Machine,    Three- 
Post    167 

Blasting     Machine,     Two- 
Post    .  165 


Page. 

Blasting  Powder,  Drying.  114 
Blasting  Powder,  Tests  of  113 

Blasting    Powders,     Com- 
position of  92 

Blasting    Powders,    Prop- 
erties of 96 

Blasting   Powder,    Storing 
and  Handling  174 

Blasting    Powder,    Under- 
ground, Handling 114 

Blasting,     Some     Precau- 
tions in   171 

Blasting,   Terms   Used   in.       7 

Blast,  Force  and  Direction 
of  a  1 

Blasts        by       Electricity, 

Firing    157 

Blasts,   Effect   of  Multiple    13 

Blasts,   Wiring  for  Multi- 
ple      161 


Boxes,   Thawing 


130 


Capacities    of    Channeling 
Machines  86 

Capacity     of     a     Blasting 
Machine  168 

Caps,  Blasting   147 

Cartridges    and    Tamping 
Materials  107 

Cartridges,   Size  of  Dyna- 
mite    323 

Channelers,    Stone    75 

Channeling  Machines,   Ca- 
pacities of   86 

Channeling  Machines, 

Drill  Steels  for 80 

Channeling  Machines,  Du- 
plex        80 


Page. 
Channeling  Machines,  Sim- 


plex 


78 


Charging     a     Drill     Hole, 

Method  of 109 

Charging  Drill  Holes  with 


Powder 


107 


Charges,     Detonators     for 
Exploding  147 

Composition     of    Blasting 
Powders    92 

Compressed  Air,   Running 

with     43 

Connections     for     Electric 
Wires    .  .  104 


Depth    and     Diameter    of 
Drill   Holes    10 

Depth  of  Tamping 109 

Detonators  for  Exploding 
Charges   147 

Diameter    and     Depth     of 
Drill  Holes 10 

Direction   and   Force  of  a 
Blast  1 

Drill  Bits  or  Steels,  Rock    51 

Drill      Hole,      Method      of 

Charging  a    109 

Drill    Hole.    Two    Electric 

Fuses  in   One 161 

Drill  Holes  . .  1 


Drill  Holes,  Charging  with 

Powder    107 

Drill  Holes.  Diameter  and 

Depth  of  10 

Drill  Holes,  Dry 46 

Drill     Holes     for     Tunnel 

Driving    23 

Drill  Holes,  Inclination  of      2 

Drill  Holes  in  Shaft  Sink- 
ing       17 

Drill    on    Mining   Column, 

Rock    41 

Drill      on      Quarry      Bar, 

Rock   39 

Drill   on   Tripod,    Rock...     35 

Drill    Steels    for   Channel- 
ing Machines    SO 

Drill     Steels.     Sizes     and 
Weights   of    55 


Page. 

Drill     Steels,     Tools     for 
Forging     61 

Drills,  Hammer  69 

Drilling      Machines,      Air 
Required   for    61 

Drilling    Machines,    Oper- 
ating       45 

Drilling  Near  Fissures  or 

Faults    28 

Driving  Large  Tunnels...     30 
Driving  Tunnel   23 

Driving       Tunnel,       Drill 

Holes  for    23 

Dry   Drill  Holes 46 

Drying  Blasting  Powder.  114 

Duplex     Channeling     Ma- 
chines       80 

Dynamite    117 

Dynamite,  Appearance  of.  122 

Dynamite  Cartridges.  Size 
of   123 

Dynamite.    Magazines    for 
the  Storage  of 175 

Dynamite.       Methods      of 

Thawing    127 

Dynamite.  Properties  of. .  124 
Dynamite,    Strength    of...  122 

Dvnamite  with   an  Active 
*    Base    121 

Dynamite  with  an  Inactive 


Base 


120 


Dynamites    and    Powders. 

Tses  for    112 


Effect  of  Multiple  Blasts..     13 
Electric  Fuses    157 

Electric      Fuses      in      One 
Drill  Hole,  Two  161 

Electric  Fuse,  Placing  the  158 

Electric     Wires,     Connec- 
tions for  164 

Electricity,    Firing   Blasts 
by    157 

Exploding     Charges,     De- 
tonators for 147 

Explosion,  Mechanical 

Work  of  an 100 


Page. 

Explosions,    Initial    Force 
of    98 

Explosive       Required, 
Amount  of   101 

Explosives,   Handling  and 

Storing    173 

Explosives,  High i?l 

Explosives,  High 117 

Explosives,   Low   91 

Explosives,  Means  of  Fir- 
ing    150 

Explosives  Used  in  Blast- 
ing       91 


Faces  in  Blasting,  Free...       4 

Faults  or  Fissures,  Drill- 
ing Near  28 

Firing  Blasts  by  Electric- 
ity      157 

Firing   Explosives,    Means 

of   150 

Firing     with     a     Blasting 
Machine   169 

Firing  with  Fuses 150 

Fissures  or  Faults,   Drill- 
ing Near   28 

Free  Faces  in  Blasting...       4 

Force  and   Direction   of  a 
Blast  1 

Force  of  Explosions,   Ini- 
tial       98 

Forging  Drill  Steels,  Tools 
for    61 

Fulminate  of  Mercury 157 

Fuse,   Description   of  a...  150 

Fuse,   Lighting  the 155 

Fuse,  Placing  the  Electric  159 

Fuses,  Electric  157 

Fuses,  Firing  with 150 

Fuses   in   One   Drill   Hole, 

Two  Electric  161 


Gelatine,  Blasting  144 

Guncotton  143 


Page. 
H 

Hammer  Drills 69 

Handling       and       Storing 
Blasting  Powder 174 

Handling      and       Storing 
Explosives    173 

Handling    Blasting    Pow- 
der Underground 114 

High  Explosives  91 

High  Explosives   117 

Hole,  Method  of  Charging 
a  Drill  109 

Holes,        Diameter        and 

Depth  of  Drill 10 

Holes,  Drill  1 

Holes,  Dry  Drill 46 

Holes  for  Tunnel  Driving, 

Drill    23 

Holes,  Inclination  of  Drill      2 

Holes    in    Shaft    Sinking, 

Drill 17 

Houses,  Steam  Thawing..  135 


Inactive    Base,     Dynamite 

with  an   120 

Inclination  of  Drill  Holes      2 
Explo- 


Initial     Force     of 
sions    


1)8 


Large  Tunnels,   Driving. 


30 

Laws  Regulating  Handling 
and  Storing  of  Explo- 
sives .................  173 

Lighting  the  Fuse  ........  155 

Low    Explosives    .........     91 


Mechanical    Work     of    an 

Explosion    100 

Machine,     Capacity     of    a 

Blasting    168 

Machine,     Firing    with    a 
Blasting    169 


Page. 

Machine,  Testing  a  Blast- 
ing    170 

Machine,  Three-Post  Blast- 
ing    167 

Machine,  Two-Post  Blast- 
ing    165 

Machinery       and       Tools, 

Rock  Drilling  35 

Machines.     Air     Required 

for  Drilling  61 

Machines,     Capacities     of 
Channeling  86 

Machines,   Drill  Steels  for 
Channeling  80 

Machines,     Duplex     Chan- 
neling       80 

Machines,  Operating  Drill- 
ing       45 

Machines,    "Pull-Up"    and 

"Push-Down"  Blasting  160 

Machines,    Simplex    Chan- 
neling       78 

Magazines  for  the  Storage 

of  Dynamite   175 

Manure       Filled        Walls, 

Thawing  Houses  with  132 

Mercury,   Fulminate  of...  147 

Method     of     Charging     a 

Drill  Hole 109 

Methods  of  Thawing  Dy- 
namite      127 

Mining       Column,       Rock 
Drill  on  41 

Multiple   Blasts,   Effect   of    13 
Multiple     Blasts,     Wiring 


for 


161 


N 


Nitroglycerine    117 

Nitroglycerine,         Proper- 
ties of  . .  118 


Page. 

Powder,  Storing  and  Han- 
dling Blasting   174 

Powder,  Tests  of  Blasting  113 

Powder          Underground. 
Handling  Blasting  ...  114 

Powders    and    Dynamites, 
Uses  for    112 

Powders,    Composition    of 
Blasting    02 

Powders,      Properties      of 

Blasting    96 

Precautions    in    Blasting, 
Some  171 

Properties      of      Blasting 
Powders    96 

Properties   of  Dynamite..  124 
Properties  of  Nitroglycer- 


ine  . 


118 


"Pull-Up"  and  "Push- 
Down"  Blasting  Ma- 
chines    169 

"Push-Down"  and  "Pull- 
Up"  Blasting  Ma- 
chines    169 


Reheaters,  Air   84 

Rock  Drill  Bits  or  Steels    51 

Rock  Drill  on  Mining  Col- 
umn        41 

Rock     Drill     on     Quarry- 
Bar  39 

Rock  Drill  on   Tripod 35 

Rock-Drilling    Tools    and 
Machinery    35 

Rock.        Sinking        Shafts 

Through    37 

Running  with  Compressed 
Air     45 

Running  with  Steam 47 


Placing  the  Electric  Fuse  159 
Powder    91 

Powder,     Charging     Drill 

Holes  with  107 

Powder,  Drying  Blasting.  114 


Shaft  Sinking,  Drill  Holes 
in   17 

Shafts      Through       Rock, 

Sinking    17 

Simplex    ^Channeling    Ma- 
chines          78 


Sinking     Shafts     Through 

Rock   17 

Size    of    Dynamite    Cart- 
ridges    123 

Sizes  and  Weights  of  Drill 

Steels    55 

Squibbing  . .  Ill 

Steam,  Running  with 47 

Steam   Thawing   Houses..  135 

Steels  for  Channeling  Ma- 
chines, Drill SO 

Steels  or  Bits,  Rock  Drill    51 

Steels,   Sizes  and  Weights 

of  Drill   55 

Steels,   Tools  for  Forging 
Drill    61 

Stone  Channelers    75 

Storage       of       Dynamite, 

Magazines   for  the 175 

Storing       and       Handling 
Blasting  Powder  174 

Storing  and  Handling  Ex- 
plosives      1T3 

Strength  of  Dynamite 122 


Tests  of  Blasting  Powder 
Thawing  Boxes   

Thawing  Dynamite,  Meth- 
ods of 

Thawing  Houses,  Steam.. 

Thawing  Houses  with  Ma- 
nure  Filled   Walls.... 

Thawing  Kettle  

Three-Post    Blasting    Ma- 
chine   

Tools       and       Machinery, 
Rock  Drilling  

Tools    for    Forging    Drill 
Steels    

Tripod,  Rock  Drill  on 

Tunnel  Driving   

Tunnel       Driving,       Drill 
Holes  for   


Tunnels,   Driving   Large.. 

Two  Electric  Fuses  in  One 
Drill  Hole 

Two-Post     Blasting     Ma- 
chine    


113 
130 

127 
135 

I.'}-* 

128 

107 

35 

01 
35 
23 

23 
30 

161 
165 


Tamping  Bags   115 

Tamping,  Depth  of 100 

and 


Tamping     Materials 
Cartridges    . 


.101 


Terms  Used  in  Blasting..       7 

Testing    a    Blasting    Ma- 
chine    170 


W 


Weights  and  Sizes  of  Drill 

Steels    55 


Wires,      Connections 
Electric    


for 


164 
Wiring  for  Multiple  Blasts  101 

Work     of    an     Explosion, 

Mechanical    100 


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